thiopental and thiobutabarbital

Marine polycyclic ether natural products continue to fascinate chemists and biologists due to their exceptionally large and complex molecular architectures and potent and diverse biological activities. Tremendous progress has been made over the past decade toward the total synthesis of marine polycyclic ether natural products. In this area, a convergent strategy for assembling small fragments into an entire molecule always plays a key role in successful total synthesis. This review describes our efforts to develop convergent strategies for the synthesis of polycyclic ethers and their application to the total synthesis of gambierol, gymnocin-A, and brevenal, and to the partial synthesis of the central part of ciguatoxins and the nonacyclic polyether skeleton of gambieric acids.

Topics: Ciguatoxins; Ethers, Cyclic; Marine Biology; Molecular Structure; Polycyclic Compounds; Thiopental

Symptoms consistent with inhalation toxicity have long been associated with Florida red tides, and various causal agents have been proposed. Research since 1981 has centered on a group of naturally occurring trans-fused cyclic polyether compounds called brevetoxins that are produced by a marine dinoflagellate known as Karenia brevis. Numerous individual brevetoxins have been identified from cultures as well as from natural bloom events. A spectrum of brevetoxin derivatives produced by chemical modification of the natural toxins has been prepared to examine the effects of functional group modification on physiologic activity. Certain structural features of natural and synthetic derivatives of brevetoxin appear to ascribe specific physiologic consequences to each toxin. Differential physiologic effects have been documented with many of the natural toxins and derivatives, reinforcing the hypothesis that metabolism or modification of toxin structures modulates both the specific toxicity (lethality on a per milligram basis) and potentially the molecular mechanism(s) of action. A series of naturally occurring fused-ring polyether compounds with fewer rings than brevetoxin, known as brevenals, exhibit antagonistic properties and counteract the effects of the brevetoxins in neuronal and pulmonary model systems. Taken together, the inhalation toxicity of Florida red tides would appear to depend on the amount of each toxin present, as well as on the spectrum of molecular activities elicited by each toxin. Toxicity in a bloom is diminished by the amount brevenal present.

Topics: Animals; Dinoflagellida; Eutrophication; Florida; Humans; Inhalation Exposure; Marine Toxins; Oxocins; Public Health; Respiratory Tract Diseases; Risk Assessment; Structure-Activity Relationship; Thiopental

Elevated renal afferent nerve (ARNA) activity or dysfunctional reno-renal reflexes via altered ARNA sensitivity contribute to hypertension and chronic kidney disease. These nerves contain mechano- and chemosensitive fibers that respond to ischemia, changes in intrarenal pressures, and chemokines. Most studies have utilized various anesthetized preparations and exclusively male animals to characterize ARNA responses. Therefore, this study assessed the impact of anesthesia, sex, and circadian period on ARNA responses and sensitivity. Multifiber ARNA recordings were performed in male and female Sprague-Dawley rats (250-400 g) and compared across decerebrate versus Inactin, isoflurane, and urethane anesthesia groups. Intrarenal artery infusion of capsaicin (0.1-50.0 μM, 0.05 mL) produced concentration-dependent increases in ARNA; however, the ARNA sensitivity was significantly greater in decerebrate versus Inactin, isoflurane, and urethane groups. Increases in renal pelvic pressure (0-30 mmHg, 30 s) produced pressure-dependent increases in ARNA; however, ARNA sensitivity was again greater in decerebrate and Inactin groups versus isoflurane and urethane. Acute renal artery occlusion (30 s) increased ARNA, but responses did not differ across groups. Analysis of ARNA responses to increased pelvic pressure between male and female rats revealed significant sex differences only in isoflurane and urethane groups. ARNA responses to intrarenal capsaicin infusion were significantly blunted at nighttime versus daytime; however, ARNA responses to increased pelvic pressure or renal artery occlusion were not different between daytime and nighttime. These results demonstrate that ARNA sensitivity is greatest in decerebrate and Inactin-anesthetized groups but was not consistently influenced by sex.

Topics: Action Potentials; Anesthetics, Inhalation; Anesthetics, Intravenous; Animals; Capsaicin; Circadian Rhythm; Decerebrate State; Dose-Response Relationship, Drug; Female; Hemodynamics; Isoflurane; Kidney; Male; Neurons, Afferent; Pressure; Rats, Sprague-Dawley; Sensory System Agents; Sex Factors; Thiopental; Time Factors; Urethane

Activation of renal sensory nerves by chemo- and mechanosensitive stimuli produces changes in efferent sympathetic nerve activity (SNA) and arterial blood pressure (ABP). Anesthesia and sex influence autonomic function and cardiovascular hemodynamics, but it is unclear to what extent anesthesia and sex impact SNA and ABP responses to renal sensory stimuli. We measured renal, splanchnic, and lumbar SNA and ABP in male and female Sprague-Dawley rats during contralateral renal infusion of capsaicin and bradykinin or during elevation in renal pelvic pressure. Responses were evaluated with a decerebrate preparation or Inactin, urethane, or isoflurane anesthesia. Intrarenal arterial infusion of capsaicin (0.1-30.0 μM) increased renal SNA, splanchnic SNA, or ABP but decreased lumbar SNA in the Inactin group. Intrarenal arterial infusion of bradykinin (0.1-30.0 μM) increased renal SNA, splanchnic SNA, and ABP but decreased lumbar SNA in the Inactin group. Elevated renal pelvic pressure (0-20 mmHg, 30 s) significantly increased renal SNA and splanchnic SNA but not lumbar SNA in the Inactin group. In marked contrast, SNA and ABP responses to every renal stimulus were severely blunted in the urethane and decerebrate groups and absent in the isoflurane group. In the Inactin group, the magnitude of SNA responses to chemo- and mechanosensory stimuli were not different between male and female rats. Thus, chemo- and mechanosensitive stimuli produce differential changes in renal, splanchnic, and lumbar SNA. Experimentally, future investigations should consider Inactin anesthesia to examine sympathetic and hemodynamic responses to renal sensory stimuli.

Topics: Anesthetics, General; Animals; Capsaicin; Female; Hemodynamics; Isoflurane; Kidney; Male; Neurons, Efferent; Rats; Rats, Sprague-Dawley; Sensory System Agents; Sex Factors; Sympathetic Nervous System; Thiopental; Touch; Urethane

Inactin is a long lasting anesthetic agent commonly used in rat studies, but is also shown to exert physiological effects such as reducing renal blood flow, glomerular filtration rate and depressing tubular transport capacity. The effect of inactin on isolated kidney mitochondria is unknown and may be important when studying related topics in anaesthetized animals. The aim of this study was to determine whether inactin exerts effects on mitochondrial function and production of reactive oxygen species. Kidney mitochondrial function and production of reactive oxygen after acutely (5 min) or longer (1.5 hour) anesthetizing rats with inactin was evaluated using high-resolution respirometry. The results demonstrate that inactin significantly improves respiratory control ratio, inhibits complex I in the mitochondrial respiratory chain, reduce both unregulated proton leak and time dependently reduce the regulated proton leak via uncoupling protein-2 and adenine nucleotide translocase. Inactin also contributes to increased mitochondrial hydrogen peroxide production. In conclusion, inactin exerts persistent effects on mitochondrial function and these profound effects on mitochondrial function should to be considered when studying mitochondria isolated from animals anesthesized with inactin.

Topics: Animals; Kidney; Male; Mitochondria; Rats; Rats, Sprague-Dawley; Reactive Oxygen Species; Thiopental; Time Factors

Anesthesia is a major confounding factor in functional MRI (fMRI) experiments attributed to its effects on brain function. Recent evidence suggests that parameters obtained with resting-state fMRI (rs-fMRI) are coupled with anesthetic depth. Therefore, we investigated whether parameters obtained with rs-fMRI, such as functional connectivity (FC), are also directly related to blood-oxygen-level-dependent (BOLD) responses.. A simple rs-fMRI protocol was implemented in a pharmacological fMRI study to evaluate the coupling between hemodynamic responses and FC under five anesthetics (α-chloralose, isoflurane, medetomidine, thiobutabarbital, and urethane). Temporal change in the FC was evaluated at 1-hour interval. Supplementary forepaw stimulation experiments were also conducted.. Under thiobutabarbital anesthesia, FC was clearly coupled with nicotine-induced BOLD responses. Good correlation values were also obtained under isoflurane and medetomidine anesthesia. The observations in the thiobutabarbital group were supported by forepaw stimulation experiments. Additionally, the rs-fMRI protocol revealed significant temporal changes in the FC in the α-chloralose, thiobutabarbital, and urethane groups.. Our results suggest that FC can be used to estimate brain hemodynamic responsiveness to stimuli and evaluate the level and temporal changes of anesthesia. Therefore, analysis of the fMRI baseline signal may be highly valuable tool for controlling the outcome of preclinical fMRI experiments. Magn Reson Med 78:1136-1146, 2017. © 2016 International Society for Magnetic Resonance in Medicine.

Topics: Anesthetics, Intravenous; Animals; Brain; Magnetic Resonance Imaging; Neurovascular Coupling; Nicotine; Oxygen; Physical Stimulation; Rats; Thiopental

Growing data support peripheral opioid antinociceptive effects, particularly in inflammatory pain models. Here, we examined the antinociceptive effects of subcutaneously administered, recently synthesized 14-O-methylmorphine-6-O-sulfate (14-O-MeM6SU) compared with morphine-6-O-sulfate (M6SU) in a rat model of inflammatory pain induced by an injection of complete Freund's adjuvant and in a mouse model of visceral pain evoked by acetic acid. Subcutaneous doses of 14-O-MeM6SU and M6SU up to 126 and 547 nmol/kg, respectively, produced significant and subcutaneous or intraplantar naloxone methiodide (NAL-M)-reversible antinociception in inflamed paws compared with noninflamed paws. Neither of these doses significantly affected thiobutabarbital-induced sleeping time or rat pulmonary parameters. However, the antinociceptive effects of higher doses were only partially reversed by NAL-M, indicating contribution of the central nervous system. In the mouse writhing test, 14-O-MeM6SU was more potent than M6SU after subcutaneous or intracerebroventricular injections. Both displayed high subcutaneous/intracerebroventricular ED50 ratios. The antinociceptive effects of subcutaneous 14-O-MeM6SU and M6SU up to 136 and 3043 nmol/kg, respectively, were fully antagonized by subcutaneous NAL-M. In addition, the test compounds inhibited mouse gastrointestinal transit in antinociceptive doses. Taken together, these findings suggest that systemic administration of the novel compound 14-O-MeM6SU similar to M6SU in specific dose ranges shows peripheral antinociception in rat and mouse inflammatory pain models without central adverse effects. These findings apply to male animals and must be confirmed in female animals. Therefore, titration of systemic doses of opioid compounds with limited access to the brain might offer peripheral antinociception of clinical importance.

Topics: Analgesics; Animals; Dose-Response Relationship, Drug; Drug Interactions; Female; Gastrointestinal Tract; Male; Mice; Morphine; Pain; Rats; Rats, Wistar; Respiration; Thiopental

Anesthetics are commonly applied in animal studies of gastrointestinal (GI) function. Different anesthetics alter smooth-muscle motility in different ways. The aim of this study is to quantify and compare non-invasively with magnetic resonance imaging (MRI) the motility patterns of the rat gut when anesthetized with inactin vs isoflurane anesthetics in the fed state.. Rats were given an oral gavage of MRI contrast agent for improved visualization of the GI tract. Two-dimensional images through the jejunum of the pre- and postanesthetized rat in the fed state were acquired every 168 ms. Image registration, segmentation, and postprocessing algorithms were applied to produce spatio-temporal maps that were used to quantify peristaltic and segmental motions in the jejunum region interspersed between periods of inactivity.. There were significantly longer periods of inactivity in the rats treated with isoflurane than in those treated with inactin (179.9 ± 22.4 s vs 17.7 ± 10.3 s). The speed of propagation and wavelength of peristalsis, and the frequency and speed of pattern switching of segmental motility, were higher (p < 0.05) in rats treated with inactin.. Isoflurane and inactin anesthetics produce significantly different motility behavior with the rat's GI tract in the fed state. Isoflurane anesthetic, results in a reduced frequency of occurrence of motility periods and an overall reduced level of motility in comparison with inactin.

Topics: Anesthetics, Inhalation; Animals; Gastrointestinal Motility; Isoflurane; Magnetic Resonance Imaging; Rats; Thiopental

Gastric motility studies are frequently conducted with anaesthetized animal models. Some studies on the same animal species have reported differences in vagal control of the stomach that could not be explained solely by slightly different experimental conditions. A possible limitation in the comparison between similar studies relates to the use of different anaesthetic agents. Furthermore, anaesthetic effects may also limit generalizations between mechanistic studies of gastric function and the gastric function of conscious animals. In the present study, we used the [(13)C]-breath test following a liquid mixed-nutrient test meal (Ensure), 1 ml) with the aim to investigate the rate of gastric emptying in animals that were either conscious or anaesthetized with either Inactin or urethane.. One week after determining the maximum (13)CO(2) concentration, time to peak [(13)C] recovery and gastric half emptying time in control, conscious rats, we repeated the experiment in the same rats anaesthetized with Inactin or urethane.. Our data show that Inactin anaesthesia prolonged the time to peak [(13)C] recovery but did not significantly reduce the maximum (13)CO(2) concentration nor delay gastric half emptying time. Conversely, urethane anaesthesia resulted in a significant slowing of all parameters of gastric emptying as measured by the maximum (13)CO(2) concentration, time to peak [(13)C] recovery and half emptying time.. Our data indicate that Inactin(R) anaesthesia does not significantly affect gastric emptying while urethane anaesthesia profoundly impairs gastric emptying. We suggest that Inactin(R), not urethane, is the more suitable anaesthetic for gastrointestinal research.

Topics: Anesthetics, Intravenous; Animals; Breath Tests; Dietary Sucrose; Enteral Nutrition; Food, Formulated; Gastric Emptying; Male; Rats; Rats, Wistar; Thiopental; Urethane; Vagus Nerve

A total synthesis of brevenal is described. The pentacyclic ether core was constructed by the intramolecular allylation of alpha-acetoxy ether and subsequent ring-closing metathesis. Both of the diene side chains were introduced by Wittig olefination and a Horner-Wadsworth-Emmons reaction, respectively, in a highly stereoselective manner.

Topics: Ethers, Cyclic; Molecular Structure; Stereoisomerism; Thiopental

The dinoflagellate Karenia brevis is known for the production of brevetoxins, a family of polycyclic ether toxins, as well as their antagonist brevenal. Further examination of organic extracts of K. brevis has uncovered yet another unprecedented cyclic ether alkaloid named brevisamide. This report describes the structure elucidation of brevisamide based on detailed MS and NMR spectral analysis, and the importance of this new compound in shedding light on the biogenesis of fused polyethers is discussed.

Topics: Alkaloids; Animals; Dinoflagellida; Ethers; Fatty Acids, Unsaturated; Magnetic Resonance Spectroscopy; Mass Spectrometry; Molecular Conformation; Pyrans; Reference Standards; Thiopental

Ciguatoxins and brevetoxins are neurotoxic cyclic polyether compounds produced by dinoflagellates, which are responsible for ciguatera and neurotoxic shellfish poisoning (NSP) respectively. Recently, brevenal, a natural compound was found to specifically inhibit brevetoxin action and to have a beneficial effect in NSP. Considering that brevetoxin and ciguatoxin specifically activate voltage-sensitive Na+ channels through the same binding site, brevenal has therefore a good potential for the treatment of ciguatera. Pacific ciguatoxin-1B (P-CTX-1B) activates voltage-sensitive Na+ channels and promotes an increase in neurotransmitter release believed to underpin the symptoms associated with ciguatera. However, the mechanism through which slow Na+ influx promotes neurosecretion is not fully understood. In the present study, we used chromaffin cells as a model to reconstitute the sequence of events culminating in ciguatoxin-evoked neurosecretion. We show that P-CTX-1B induces a tetrodotoxin-sensitive rise in intracellular Na+, closely followed by an increase in cytosolic Ca2+ responsible for promoting SNARE-dependent catecholamine secretion. Our results reveal that brevenal and beta-naphtoyl-brevetoxin prevent P-CTX-1B secretagogue activity without affecting nicotine or barium-induced catecholamine secretion. Brevenal is therefore a potent inhibitor of ciguatoxin-induced neurotoxic effect and a potential treatment for ciguatera.

Topics: Animals; Antidotes; Calcium; Catecholamines; Cattle; Chromaffin Cells; Ciguatera Poisoning; Ciguatoxins; Neurosecretion; Sodium; Sodium Channels; Thiopental

Macula densa (MD) cells express the Na(+)/H(+) exchanger (NHE) isoform NHE2 at the apical membrane, which may play an important role in tubular salt sensing through the regulation of cell volume and intracellular pH. These studies aimed to determine whether NHE2 participates in the MD control of renin synthesis. Renal renin content and activity and elements of the MD signaling pathway were analyzed using wild-type (NHE2(+/+)) and NHE2 knockout (NHE2(-/-)) mice. Immunofluorescence studies indicated that NHE2(-/-) mice lack NHE3 at the MD apical membrane, so the other apical NHE isoform has not compensated for the lack of NHE2. Importantly, the number of renin-expressing cells in the afferent arteriole in NHE2(-/-) mice was increased approximately 2.5-fold using renin immunohistochemistry. Western blotting confirmed approximately 20% higher renal cortical renin content in NHE2(-/-) mice compared with wild type. No-salt diet for 1 wk significantly increased renin content and activity in NHE2(+/+) mice, but the response was blunted in NHE2(-/-) mice. Renal tissue renin activity and plasma renin concentration were elevated three- and twofold, respectively, in NHE2(-/-) mice compared with wild type. NHE2(-/-) mice also exhibited a significantly increased renal cortical cyclooxygenase-2 (COX-2) and microsomal prostaglandin E synthase (mPGES) expression, indicating MD-specific mechanisms responsible for the increased renin content. Significant and chronic activation of ERK1/2 was observed in MD cells of NHE2(-/-) kidneys. Removal of salt or addition of NHE inhibitors to cultured mouse MD-derived (MMDD1) cells caused a time-dependent activation of ERK1/2. In conclusion, the NHE2 isoform appears to be important in the MD feedback control of renin secretion, and the signaling pathway likely involves MD cell shrinkage and activation of ERK1/2, COX-2, and mPGES, all well-established elements of the MD-PGE(2)-renin release pathway.

Topics: Animals; Blotting, Western; Cyclooxygenase 2; DNA Primers; Kidney; Kidney Cortex; Mice; Mice, Knockout; Renin; Sodium-Hydrogen Exchangers; Thiopental

Total synthesis of (-)-brevenal, a novel marine polycyclic ether natural product, is described. Highly efficient and scalable entries to the AB-ring exo-olefin and the DE-ring enol phosphate and a rapid construction of the C-ring by means of our Suzuki-Miyaura coupling-based strategy realized a concise synthesis of the pentacyclic skeleton of (-)-brevenal. The present synthesis is considerably more efficient than our previous synthesis (longest linear sequence: 50 steps from 2-deoxy-d-ribose).

Topics: Ethers; Polymers; Stereoisomerism; Thiopental; Time Factors

The hemodynamic effects of a series of potent and selective 4-aminopyridine carboxamide-based pan-JNK inhibitors were assessed in an anesthetized rat model. The effects of these agents on mean arterial pressure, heart rate, cardiac contractility, and peripheral vascular resistance are described, and the implication for targeting protein kinases in metabolic diseases is discussed.

Topics: Aminopyridines; Anesthesia; Anesthetics; Animals; Blood Pressure; Enzyme Inhibitors; Heart Rate; Male; MAP Kinase Kinase 4; Metabolic Diseases; Myocardial Contraction; Rats; Rats, Sprague-Dawley; Structure-Activity Relationship; Thiopental; Vascular Resistance; Ventricular Function, Left

Brevetoxins (PbTxs) are highly potent trans-syn polyether neurotoxins produced during blooms of several species of marine dinoflagellates, most notably Karenia brevis. These neurotoxins act on voltage-sensitive sodium channels prolonging the active state. During red tides, the commercial fishing and tourism industries experience millions of dollars of lost revenue. Human consumption of shellfish contaminated with PbTxs results in neurotoxic shellfish poisoning (NSP). Additionally, blooms of K. brevis are potentially responsible for adverse human health effects such as respiratory irritation and airway constriction in coastal residents. There is little information regarding the full range of potential toxic effects caused by PbTxs. Recent evidence suggests that PbTxs are genotoxic substances. The purpose of this study was to determine if PbTxs could induce chromosomal aberrations and inhibit cellular proliferation in CHO-K1-BH4 cells, and if so, could the damage be negated or reduced by the PbTx antagonist brevenal. Results from the chromosomal aberrations assay demonstrated that PbTxs are potent inducers of CHO-K1-BH4 chromosome damage. Results from the inhibition of cellular proliferation assays demonstrated that PbTxs inhibit the ability of CHO-K1-BH4 cells to proliferate, an effect which can be reduced with brevenal.

Topics: Animals; Cell Proliferation; CHO Cells; Chromosome Aberrations; Cricetinae; Dinoflagellida; Marine Toxins; Mitomycin; Mutagenicity Tests; Nucleic Acid Synthesis Inhibitors; Oxocins; Thiopental

Total synthesis of the proposed structure of brevenal, a natural marine polycyclic ether product, has been accomplished. The synthesis features (i) convergent synthesis of the pentacyclic polyether skeleton using our developed Suzuki-Miyaura coupling strategy and (ii) construction of the multi-substituted dienal side chain by CuTC-mediated Stille reaction. Comparison of the NMR data of the synthetic compound with those reported for the natural product revealed that the proposed structure of brevenal needs to be revised.

Topics: Molecular Structure; Thiopental

Total synthesis of structure 1 originally proposed for brevenal, a nontoxic polycyclic ether natural product isolated from the Florida red tide dinoflagellate, Karenia brevis, was accomplished. The key features of the synthesis involved (i) convergent assembly of the pentacyclic polyether skeleton based on our developed Suzuki-Miyaura coupling chemistry and (ii) stereoselective construction of the multi-substituted (E,E)-dienal side chain by using copper(I) thiophen-2-carboxylate (CuTC)-promoted modified Stille coupling. The disparity of NMR spectra between the synthetic material and the natural product required a revision of the proposed structure. Detailed spectroscopic comparison of synthetic 1 with natural brevenal, coupled with the postulated biosynthetic pathway for marine polyether natural products, suggested that the natural product was most likely represented by 2, the C26 epimer of the proposed structure 1. The revised structure was finally validated by completing the first total synthesis of (-)-2, which also unambiguously established the absolute configuration of the natural product.

Topics: Magnetic Resonance Spectroscopy; Molecular Conformation; Sensitivity and Specificity; Stereoisomerism; Thiopental

We evaluated the effect of the inhalant anesthetic isoflurane and the injectable combination of anesthetics ketamine/inactin on cardiac function by measuring left ventricular (LV) pressure in situ during control conditions and during beta-adrenergic stimulation with isoproterenol (ISO). The control heart rate (HR) and the maximal rate of contraction were significantly higher in the isoflurane group, but there was no difference in the rate of relaxation. During the ISO (0.32 ng g body wt(-1) min(-1)) stimulation the developed pressure (DP) increased 9.8 +/- 1.8% (n = 11) in the ketamine/inactin group and was unchanged in the isoflurane group. The HR increased 28.4 +/- 4.8% (n = 11) in the ketamine/inactin group and only 3.4 +/- 0.6% (n = 11) in the isoflurane group. The rate of contraction increased 103.2 +/- 9.3% (n = 11) and 13.6 +/- 4.6% (n = 11) in the ketamine/inactin and isoflurane groups, respectively. At this dose of ISO the rate of relaxation did not change significantly. In control conditions there was no difference in levels of cAMP between the groups (2.29 +/- 0.25 pmol/mg protein (n = 5) in the ketamine/inactin group and 2.79 +/- 0.35 pmol/mg protein (n = 6) in the isoflurane group). However, during the ISO stimulation the cAMP level increased only in the ketamine/ inactin group of animals (3.50 +/- 0.30 pmol/mg protein; n = 5). This level was significantly higher than the level in the isoflurane group stimulated with ISO (2.22 +/- 0.30 pmol/mg protein; n = 6). In summary, our results indicate that the anesthetics differ significantly in the extent of depression of the basal and beta-adrenergic stimulated state with the second messenger cAMP playing a prominent role.

Topics: Adrenergic beta-Agonists; Anesthetics, Combined; Anesthetics, Inhalation; Anesthetics, Intravenous; Animals; Cyclic AMP; Female; Heart Rate; Isoflurane; Isoproterenol; Ketamine; Male; Mice; Myocardial Contraction; Myocardium; Thiopental; Ventricular Function, Left; Ventricular Pressure

Brevenal is a nontoxic short-chain trans-syn polyether that competes with brevetoxin (PbTx) for the active site on voltage-sensitive sodium channels. The PbTxs are highly potent polyether toxins produced during blooms of several species of marine dinoflagellates, most notably Karenia brevis. Blooms of K. brevis have been associated with massive fish kills, marine mammal poisoning, and are potentially responsible for adverse human health effects such as respiratory irritation and airway constriction in beach-goers. Additionally, the consumption of shellfish contaminated with PbTxs results in neurotoxic shellfish poisoning (NSP). The purpose of the present study was to determine whether PbTx could induce DNA damage in a human cell type, the lymphocyte, and if so, whether the damage could be antagonized or ameliorated by brevenal, a brevetoxin antagonist. The DNA damage may occur through both endogenous and exogenous physiological and pathophysiological processes. Unrepaired or erroneously repaired DNA damage may result in gene mutation, chromosome aberration, and modulation of gene regulation, which have been associated with immunotoxicity and carcinogenesis. A single-cell gel electrophoresis assay, or comet assay, was used to determine and compare DNA damage following various treatments. The data were expressed as tail moments, which is the percentage of DNA in the tail multiplied by the length between the center of the head and center of the tail (in arbitrary units). The negative control tail moment was 29.2 (SE=+/-0.9), whereas the positive control (hydrogen peroxide) was 72.1 (1.5) and solvent (ethanol) was 24.2 (2.1). The PbTx-2 (from Sigma, St. Louis, MO, USA), 10(-8) M was 41.3 (3.6), PbTx-9 (Sigma), 10(-8) M was 57.0 (5.3), PbTx-2 (from University of North Carolina at Wilmington, UNCW), 10(-8) M was 49.4 (9.9), and PbTx-3 (UNCW), 10(-8) M was 64.0 (6.4). 1.0 microg/ml brevenal applied 1 h before the PbTxs protected the lymphocytes from DNA damage; PbTx-2 (Sigma), 31.3 (2.1); PbTx-9 (Sigma), 35.5 (2.9); PbTx-2 (UNCW), 33.9 (1.4); PbTx-3 (UNCW), 34.9 (1.25). The tail moment for 1.0 mug/ml brevenal alone was 30.8 (2.6). The results indicate that extensive genotoxic damage is induced by PbTx-2 and 9 (Sigma), and PbTx-2 and 3 (UNCW) in normal human lymphocytes, which is fully antagonized by brevenal. This suggests that the immune systems of individuals exposed to PbTx during harmful algal bloom (HAB) events may be at risk.

Topics: Animals; Cells, Cultured; Dinoflagellida; DNA Damage; Humans; Lymphocytes; Marine Toxins; Neurotoxins; Oxocins; Thiopental

1. Prostaglandin D (DP) receptor agonists have been shown to induce hypotension in rat models, possibly via peripheral vasodilation. However, it is not known which tissues and organs are most responsive. 2. In the present study, BW245C, a DP receptor-selective agonist, was administered to Inactin (Sigma, St Louis, MO, USA)-anaesthetized rats. Animals received three serial i.v. infusions (17 min each) of either BW245C (escalating doses of 0.3, 3 and 30 microg/kg; n=6) or vehicle (6% ethanol in normal saline; n=6). Mean arterial pressure (MAP) and heart rate were monitored continuously and regional blood flow was determined by the radionuclide-labelled microsphere method at baseline and at the end of each infusion. 3. It was found that BW245C dose-dependently reduced MAP; blood flow increased in forelimb skeletal muscle and skin, resulting in decreases in the regional vascular resistance (RVR) of skeletal muscle to -6+/-13, -53+/-11 and -68+/-6% of baseline following 0.3, 3 and 30 microg/kg BW245C, respectively (P<0.05 vs vehicle treatment for the two higher doses), and skin to -29+/-8, -55+/-8 (P<0.05) and -30+/-16% of baseline, respectively. Relative to vehicle, blood flow and RVR for brain, heart, lung, liver, stomach and kidney were not significantly affected by BW245C. 4. These results demonstrate that the hypotension resulting from DP receptor activation in the rat is mediated primarily through vasodilation of arterioles of skeletal muscle independent of changes in blood flow to vital organs.

Topics: Anesthesia; Anesthetics, Intravenous; Animals; Blood Pressure; Dose-Response Relationship, Drug; Hemodynamics; Hydantoins; Infusions, Intravenous; Injections, Intraperitoneal; Male; Muscle, Skeletal; Rats; Rats, Sprague-Dawley; Receptors, Immunologic; Receptors, Prostaglandin; Regional Blood Flow; Skin; Thiopental; Vascular Resistance; Vasodilation; Vasodilator Agents

1. Florida red tides produce profound neurotoxicity that is evidenced by massive fish kills, neurotoxic shellfish poisoning, and respiratory distress. Red tides vary in potency, potency that is not totally governed by toxin concentration. The purpose of the study was to understand the variable potency of red tides by evaluating the potential for other natural pharmacological agents which could modulate or otherwise reduce the potency of these lethal environmental events. 2. A synaptosome binding preparation with 3-fold higher specific brevetoxin binding was developed to detect small changes in toxin binding in the presence of potential antagonists. Rodent brain labeled in vitro with tritiated brevetoxin shows high specific binding in the cerebellum as evidenced by autoradiography. Synaptosome binding assays employing cerebellum-derived synaptosomes illustrate 3-fold increased specific binding. 3. A new polyether natural product from Florida's red tide dinoflagellate Karenia brevis, has been isolated and characterized. Brevenal, as the nontoxic natural product is known, competes with tritiated brevetoxin for site 5 associated with the voltage-sensitive sodium channel (VSSC). Brevenal displacement of specific brevetoxin binding is purely competitive in nature. 4. Brevenal, obtained from either laboratory cultures or field collections during a red tide, protects fish from the neurotoxic effects of brevetoxin exposure. 5. Brevenal may serve as a model compound for the development of therapeutics to prevent or reverse intoxication in red tide exposures.

Topics: Animals; Binding, Competitive; Biological Assay; Cerebellum; Cyprinodontiformes; Dinoflagellida; Ethers; Male; Marine Toxins; Mice; Molecular Structure; Oxocins; Polymers; Presynaptic Terminals; Radioligand Assay; Sodium Channel Blockers; Sodium Channels; Synaptic Transmission; Synaptosomes; Thiopental

Mice that lack or over-express a gene of interest are important tools for unraveling gene function. The determination of single nephron function by micropuncture or precise determination of glomerular filtration rate (GFR) by inulin clearance method require experiments under anesthesia. A good anesthetic protocol should allow for reasonable and stable glomerular and tubular function. The aim of this study was to compare the commonly used thiobutabarbital (TBB) versus alpha-chloralose (CHL) anesthesia with regard to absolute levels and the stability of blood pressure, heart rate, and kidney function. Male CD1 mice were anesthetized with TBB (100 mg/kg body weight i.p.) or CHL (120 mg/kg body weight i.p.), plus ketamine (100 mg/kg body weight i.m.) given to every mouse for analgesia. After preparation for clearance experiments, two 30-min urine collections were performed at periods 1 and 2 (P1 and P2). It was observed that heart rate and mean arterial blood pressure did not differ between TBB ( n=9) vs. CHL ( n=9) and were stable through P1 and P2. In CHL, GFR as well as fractional excretion of fluid, Na(+) and K(+) were stable from P1 to P2 (P1: 190+/-15 microl/min, 1.6+/-0.2%, 0.7+/-0.1%, 35+/-5%; percent change in P2: 1+/-6, 26+/-10, 29+/-15, 6+/-10 respectively). In TBB, GFR was significantly greater vs. CHL in P1 and did not significantly change in P2 (246+/-8 microl/min, p<0.05; percent change: -6.5+/-4). Fractional excretion of fluid, Na(+) and K(+) were not significantly different vs. CHL in P1, but significantly increased in P2 (P1: 1.5+/-0.2%, 1.1+/-0.2%, 31+/-3%; percent change in P2: 122+/-23, 128+/-21 and 29+/-6 respectively; each p<0.05 vs. P1). In conclusion, mice under both anesthetic regimens present reasonable and stable blood pressure and reasonable kidney function, but kidney reabsorption is more stable under CHL than under TBB anesthesia, which may facilitate study of the response in kidney function to acute interventions.

Topics: Anesthesia; Animals; Chloralose; Glomerular Filtration Rate; Kidney; Male; Mice; Thiopental

The effects of oxytocin on renin secretion by denervated kidney were investigated in vivo, by infusing the peptide directly into the renal artery of anaesthetized rats. Renin secretion was calculated by the renal veno-arterial difference in plasma renin activity multiplied by renal plasma flow. The intra-renal arterial (i.r.a.) infusion of oxytocin (1.5 or 15 ng/kg/min, 10 min) induced a sixfold increase in renin secretion as compared to vehicle-treated controls, without effects on renal blood flow, mean arterial blood pressure, glomerular filtration rate or natriuresis. The effect of oxytocin (1.5 ng/kg/min) was prevented by pretreatment with an oxytocin receptor antagonist, desGly-NH(2),d(CH(2))(5)[D-Tyr(2),Thr(4),Orn(8)]vasotocin] (5.6 microg/kg bolus i.v. 20 min before oxytocin infusion, followed by 2.8 microg/kg/min i.r.a.). Nadolol (2.5 mg/kg i.v.), a beta-adrenoceptor antagonist, also blocked the oxytocin-induced increase in renin secretion. These results show that oxytocin is able to stimulate renin release by activating oxytocin receptors but that beta-adrenoceptors also seem to be involved.

Topics: Anesthetics; Animals; Denervation; Kidney; Male; Oxytocin; Rats; Rats, Sprague-Dawley; Renal Artery; Renin; Thiopental

Previous studies have indicated that angiotensin II (Ang II) concentrations in renal interstitial fluid are much higher than plasma levels. In the present study, we performed experiments to explore renal interstitial fluid concentrations of Ang I and Ang II further and to determine whether these levels are altered by acute arterial infusion of an ACE inhibitor (enalaprilat) or by volume expansion. Microdialysis probes (molecular weight cutoff point: 30 000 Da) were implanted in the renal cortex of anesthetized rats and were perfused at a rate of 2 microL/min. Using relative equilibrium rates, the basal renal interstitial fluid Ang II concentration averaged 3.07+/-0.43 nmol/L, a value much higher than the plasma Ang II concentration of 107+/-8 pmol/L (n=7). Interstitial fluid Ang I concentrations (0.84+/-0.04 nmol/L) were consistently lower than the Ang II concentrations but higher than the plasma Ang I concentrations (112+/-14 pmol/L). Intra-arterial infusion of enalaprilat (7.5 micromol/kg/min, n=5) for 120 minutes resulted in a significant decrease in mean arterial pressure (from 114+/-4 to 68+/-4 mm Hg) along with reductions in plasma and renal ACE activity (by -99% and -52%, respectively). Enalaprilat resulted in a significant increase in plasma Ang I from 133+/-21 to 1167+/-328 pmol/L and a decrease in plasma Ang II from 110+/-12 to 67+/-9 pmol/L. During enalaprilat infusion, interstitial fluid concentration of Ang I was significantly increased from 0.78+/-0.06 to 0.97+/-0.08 nmol/L; however, Ang II concentrations were not altered significantly (3.67+/-0.28 versus 3.67+/-0.25 nmol/L). Acute volume loading with Ringer's solution containing 1% bovine serum albumin at a rate of 150 microL/min for 2 hours (6% to 7% of body weight) lowered plasma concentrations of Ang I from 110+/-23 to 16+/-2 pmol/L and Ang II from 100+/-23 to 36+/-6 pmol/L; however, renal interstitial fluid concentrations of Ang I and Ang II were not altered significantly during volume expansion (Ang I, from 0.77+/-0.05 to 0.69+/-0.03 nmol/L; Ang II, from 3.76+/-0.43 to 3.59+/-0.39 nmol/L, n=5). These data indicate that renal interstitial fluid concentrations of Ang I and Ang II are substantially higher than the corresponding plasma concentrations. Furthermore, the fact that the high interstitial fluid concentrations of Ang II are not responsive to acute ACE inhibition or volume expansion suggests the compartmentalization and independent regulation of renal interstitial fluid Ang II.

Topics: Anesthesia; Angiotensin I; Angiotensin II; Angiotensin-Converting Enzyme Inhibitors; Animals; Antihypertensive Agents; Blood Pressure; Blood Volume; Enalapril; Extracellular Space; Infusions, Intra-Arterial; Kidney; Microdialysis; Rats; Rats, Sprague-Dawley; Thiopental

1. This study examined the role of endothelin ET(A) and ET(B) receptors on haemodynamic compensation following haemorrhage (-17.5 ml kg(-1)) in thiobutabarbitone-anaesthetized rats. Rats were divided into four groups (n=6 each): time-control, haemorrhage-control, haemorrhage after treatment with FR 139317 (ET(A)-receptor antagonist), and haemorrhage after treatment with BQ-788 (ET(B)-receptor antagonist). 2. In the time-control rats, there were no significant changes in any haemodynamics for the duration of the experiments. Relative to the time-control rats, rats given haemorrhage had reduced mean arterial pressure (MAP), cardiac output (CO) and mean circulatory filling pressure (MCFP), but increased systemic vascular resistance (R(SV)). Venous resistance (R(V)) was slightly (but insignificantly) reduced by haemorrhage. MAP, however, gradually returned towards baseline (-17+/-4 and -3+/-2 mmHg at 10 and 60 min after haemorrhage, respectively) as a result of a further increase in R(SV). 3. Pre-treatment with FR 139317 (i.v. 1 mg kg(-1), followed by 1 mg kg(-1) h(-1)) accentuated haemorrhage-induced hypotension through abolition of the increase in R(SV). FR 139317 did not modify haemorrhage-induced changes in CO, MCFP and R(V). 4. Pre-treatment of BQ-788 (3 mg kg(-1)) did not affect MAP or MCFP following haemorrhage; however, CO was lower, and R(SV) as well as R(V) were higher relative to the readings in the haemorrhaged-control rats. 5. These results show that following compensated haemorrhage, ET maintains arterial resistance and blood pressure via the activation of ET(A) but not ET(B) receptors.

Topics: Anesthetics; Animals; Azepines; Blood Volume; Endothelin Receptor Antagonists; Hematocrit; Hemodynamics; Hemorrhage; Indoles; Male; Oligopeptides; Piperidines; Rats; Rats, Sprague-Dawley; Receptor, Endothelin A; Receptor, Endothelin B; Receptors, Endothelin; Thiopental

The present study used activation of the c-Fos oncogene protein within neurons in the dorsal vagal complex (DVC) as a marker of neuronal excitation in response to systemic endotoxin challenge [i.e. , lipopolysaccharide (LPS)]. Specifically, we investigated whether vagal connections with the brain stem are necessary for LPS cytokine- induced activation of DVC neurons. Systemic exposure to LPS elicited a significant activation of c-Fos in neurons in the nucleus of the solitary tract (NST) and area postrema of all thiobutabarbital-anesthetized rats examined, regardless of the integrity of their vagal nerves. That is, rats with both vagi cervically transected were still able to respond with c-Fos activation of neurons in the DVC. Unilateral cervical vagotomy produced a consistent but small reduction in c-Fos activation in the ipsilateral NST of all animals within this experimental group. Given that afferent input to the NST is exclusively excitatory, it is not surprising that unilateral elimination of all vagal afferents would diminish NST responsiveness (on the vagotomized side). These data lead us to conclude that the NST itself is a primary central nervous system detector of cytokines.

Topics: Anesthetics; Animals; Lipopolysaccharides; Male; Neurons, Afferent; Neurons, Efferent; Proto-Oncogene Proteins c-fos; Rats; Rats, Long-Evans; Solitary Nucleus; Thiopental; Tumor Necrosis Factor-alpha; Vagotomy; Vagus Nerve

The subject of this investigation was to study influence of the intestinal motility on absorption of 3-o-methyl-D-glucose (3-OMG), mannitol and polyethylene glycol (PEG 4000), used as absorption route markers, while monitoring cardiovascular parameters in an intestinal in situ model in rats. Rats were anaesthetized with Inactin(R) and Rapinovet(R). A segment of duodenum, approximately 10 cm, was perfused single-pass with saline containing unlabelled and radioactive 3-OMG, PEG 4000 or mannitol. The PEG 4000 was recovered almost completely in the intestinal perfusate suggesting an intact mucosal integrity. Most animals exhibited an intestinal contractile activity resembling fed motility except seven out of 19 given Rapinovet, which showed a 'burst-type' pattern resembling migrating motor complex (MMC). Absorption of 3-OMG in rats with MMC-like motility appears to be lower than in rats with fed-like motility, while no such difference was seen for mannitol. Moreover, there was a positive correlation (r 2=0.75) between intestinal activity (fed) and absorption of 3-OMG, but not with absorption of mannitol. The carrier-mediated absorption of 3-OMG was not only influenced by intestinal motility, but also by its pattern. This was not observed with mannitol, which is passively absorbed.

Topics: 3-O-Methylglucose; Anesthesia; Anesthetics; Animals; Blood Pressure; Drug Combinations; Duodenum; Eating; Food Deprivation; Gastrointestinal Motility; Heart Rate; Intestinal Absorption; Male; Mannitol; Methohexital; Models, Animal; Polyethylene Glycols; Propofol; Rats; Rats, Sprague-Dawley; Thiopental

Melatonin is released from intestinal enterochromaffin cells and from the pineal gland, but its role in gastrointestinal function is largely unknown. Our aim was to study the involvement of intestinal and central nervous melatonin in the neurohumoral control of the duodenal mucosa-protective bicarbonate secretion. Working in anesthetized rats, we cannulated a 12-mm segment of duodenum with an intact blood supply and titrated the local bicarbonate secretion with pH-stat. Melatonin and receptor ligands were supplied to the duodenum by close intra-arterial infusion. Even at low doses, melatonin and the full agonist 2-iodo-N-butanoyl-5-methoxytryptamine increased duodenal bicarbonate secretion. Responses were inhibited by the predominantly MT2-selective antagonist luzindole but not by prazosin, acting at MT3 receptors. Also, luzindole almost abolished the marked rise in secretion induced by intracerebroventricular infusion of the adrenoceptor agonist phenylephrine. This response was also abolished by sublaryngeal ligation of all nerves around the carotid arteries. However, it was insensitive to truncal vagotomy alone or sympathectomy alone and was unaffected by removal of either the pineal gland or pituitary gland. Thus, melatonin stimulates duodenal bicarbonate secretion via action at enterocyte MT2-receptors and mediates neural stimulation of the secretion.

Topics: Adrenocorticotropic Hormone; Animals; Bicarbonates; Blood Pressure; Circadian Rhythm; Corticotropin-Releasing Hormone; Duodenum; Enterochromaffin Cells; gamma-MSH; Hypophysectomy; Injections, Intra-Arterial; Injections, Intraventricular; Intestinal Mucosa; Melatonin; Neurosecretion; Phenylephrine; Pineal Gland; Prazosin; Protein Isoforms; Rats; Rats, Inbred Lew; Rats, Sprague-Dawley; Receptors, Cell Surface; Receptors, Cytoplasmic and Nuclear; Receptors, Melatonin; Tetrahydronaphthalenes; Thiopental; Tryptamines; Vagotomy

The renal vascular response to vasopressin and its modulation were evaluated in vivo by infusing the peptide directly into the renal artery of anaesthetized rats. The intra-renal artery (i.r.a) infusion of vasopressin induced a dose-dependent decrease in renal blood flow. Vasoconstriction was obvious at a dose of 3 ng/kg per min and reached a maximum at 100 ng/kg per min. The dose required for a half-maximal response (ED50) was 24+/-4 ng/kg per min (mean+/-SEM, n=8), corresponding to an estimated concentration in renal arterial blood required for a half-maximal response (EC50) of 1.9+/-0.6 nM. Thiobutabarbitone anaesthesia markedly increased plasma vasopressin concentration. This increase was prevented partially by hypotonic hydration of the rats without any change in the renal vascular response to exogenous vasopressin. Vasopressin-induced vasoconstriction dose/response curves were similar in homozygous and heterozygous Brattleboro rats. Infusion of desmopressin (1-1000 ng/kg per min, i.r.a.), a vasopressin V2 receptor-selective agonist, failed to induce renal vasodilation or vasoconstriction. In the presence of SR 49059 (1 mg/kg i.v.), a vasopressin V1A receptor antagonist that completely abolished the vasopressin-induced renal vasoconstriction, desmopressin again failed to induce vasodilation. Inhibition of nitric oxide synthase by N(omega)-nitro-L-arginine (L-NNA, 100 microg/kg for 10 min and 7.5 microg/kg per min, i.r.a.) enhanced vasopressin-induced renal vasoconstriction (EC50 0.6+/-0.1 nM, P<0.05). In contrast, cyclooxygenase blockade by indomethacin (5 mg/kg, i.v.) neither modified the vasopressin-induced decrease in renal blood flow nor altered the potentiation of vasoconstriction by L-NNA. These results show that the constrictor response of the rat renal vascular bed in vivo is observed only with high local concentrations of vasopressin. This hyporeactivity in vivo was not explained by an anaesthesia-elicited increase in endogenous vasopressin, nor by a modulatory effect linked to V2 receptor activation or prostanoid release. In contrast, NO release contributed to the attenuation of vasopressin-induced renal vasoconstriction.

Topics: Anesthesia; Animals; Antidiuretic Hormone Receptor Antagonists; Deamino Arginine Vasopressin; Dose-Response Relationship, Drug; Drug Interactions; Hemodynamics; Hormone Antagonists; Indoles; Male; Nitric Oxide; Pyrrolidines; Rats; Rats, Brattleboro; Rats, Sprague-Dawley; Renal Agents; Renal Artery; Renal Circulation; Thiopental; Vasoconstriction; Vasodilator Agents; Vasopressins

Rodents are the unique species carrying duplicated angiotensin (Ang) type 1 (AT1) receptor genes, Agtr1a and Agtr1b. After separately generating Agtr1a and Agtr1b null mutant mice by gene targeting, we produced double mutant mice homozygous for both Agtr1a and Agtr1b null mutation (Agtr1a-/-; Agtr1b-/-) by mating the single gene mutants. Agtr1a-/-, Agtr1b-/- mice are characterized by normal in utero survival but decreased ex utero survival rate. After birth they are characterized by low body weight gain, marked hypotension, and abnormal kidney morphology including delayed maturity in glomerular growth, hypoplastic papilla, and renal arterial hypertrophy. These abnormal phenotypes are quantitatively similar to those found in mutant mice homozygous for the angiotensinogen gene (Agt-/-), indicating that major biological functions of endogenous Ang elucidated by the abnormal phenotypes of Agt-/- are mediated by the AT1 receptors. Infusion of Ang II, AT1 blockers, or an AT2 blocker was without effect on blood pressure in Agtr1a-/-; Agtr1b-/- mice, indicating that AT2 receptor does not exert acute depressor effects in these mice lacking AT1 receptors. Also, unlike Agt-/- mice, some Agtr1a-/-; Agtr1b-/- mice have a large ventricular septum defect, suggesting that another receptor such as AT2 is functionally activated in Agtr1a-/-, Agtr1b-/- mice.

Topics: Adrenal Glands; Anesthetics; Angiotensin II; Angiotensinogen; Animals; Benzimidazoles; beta-Galactosidase; Biphenyl Compounds; Blood Pressure; Imidazoles; Infusions, Intravenous; Kidney; Losartan; Mice; Mice, Knockout; Myocardium; Phenotype; Pyridines; Receptor, Angiotensin, Type 1; Receptors, Angiotensin; Saralasin; Staining and Labeling; Tetrazoles; Thiopental; Zygote

Sodium azide (NaN3, AZ) is a potent inhibitor and uncoupler of oxidative phosphorylation as well as a nitrovasodilator after being converted to nitric oxide (NO). We studied the effect of intratubular application of AZ on loop of Henle reabsorption and tubuloglomerular feedback (TGF) employing renal micropuncture experiments in nephrons with superficial glomeruli of anesthetized Munich-Wistar-Fromter rats. During perfusion of Henle's loop downstream from an obstructing wax block, AZ (3x10(-5) mol/l and 3x10(-4) mol/l) concentration-dependently increased early distal tubular flow rate and sodium and potassium ion concentration (V(ED), [Na+]ED, [K+]ED). In comparison, application of furosemide (10(-4) mol/l), the action of which is restricted to the water-impermeable thick ascending limb of Henle's loop (TALH) and the macula densa, similarly increased [Na+]ED and [K+]ED, but did not affect V(ED). The effect of AZ on loop of Henle reabsorption appeared to be predominantly localized upstream to the TALH since (1) AZ significantly inhibited net fluid reabsorption (the latter being completely abolished at 3x10(-4) mol/l), (2) the effect of AZ on [Na+]ED and [K+]ED could be mimicked by perfusing the Henle's loop at a flow rate that caused a comparable increase in V(ED) (reflecting a comparable load to TALH), and (3) the effects of AZ and furosemide were additive. In spite of the increase in [Na+]ED and [K+]ED, intratubular application of AZ caused a concentration-dependent inhibition of TGF response, the latter being assessed as the fall in early proximal tubular stop flow pressure during perfusion of Henle's loop at increasing flow rate. Like AZ and furosemide, the NO donor sodium nitroprusside (10(-4) mol/l) blunted the TGF response, but in contrast to furosemide or AZ, it caused a minor decrease in V(ED), without changing [Na+]ED or [K+]ED. The inhibitory effect of AZ on TGF was abolished by the NO scavenger carboxy PTIO. In summary, AZ inhibits both reabsorption in the water-permeable segment of Henle's loop and the TGF response. The effect on reabsorption may be linked to metabolic inhibition rather than NO release, whereas the blunted TGF response appears to involve conversion to NO.

Topics: Absorption; Anesthesia; Animals; Diuretics; Enzyme Inhibitors; Feedback; Furosemide; Loop of Henle; Male; Nitric Oxide; Potassium; Punctures; Rats; Sodium; Sodium Azide; Thiopental

The role of body and hindlimb temperature in the control of blood flow in nerve and muscle was assessed by laser Doppler flowmetry. Following surgical exposure of nerve, initial measurements were taken for 5 min at hindlimb temperatures of 30-31 degrees C. A second set of identical measurements was then made either with or without warming to 37 degrees C. Without warming, nerve laser Doppler flow (NLDF) increased by 14.5+/-3.2% (mean+/-SEM) but, with warming, decreased by 40.9+/-8.2%. In contrast, adduccamerontor magnus muscle laser Doppler flow (MLDF) decreased without warming (14.7+/-1.0%) and increased with warming (20.4+/-12.8%). Because blood pressure was not significantly altered by changes in hindlimb temperature, the patterns of changes in vascular conductance (laser Doppler flow/blood pressure) were not significantly different from that seen with NLDF and MLDF. Thus, warming to physiological temperatures was associated with decreased NLDF and vascular conductance and increased MLDF and vascular conductance. These data may have implications for the interpretation of nerve blood flow data obtained at different hindlimb temperatures.

Topics: Adjuvants, Anesthesia; Animals; Body Temperature; Female; Hindlimb; Hypothermia; Laser-Doppler Flowmetry; Muscle, Skeletal; Neural Conduction; Pentobarbital; Rats; Rats, Sprague-Dawley; Regional Blood Flow; Sciatic Nerve; Thiopental

Several investigators have demonstrated that the opioid pathway is involved in tissue preservation during hypoxia or ischemia and that this protection is mediated via the delta (delta)-opioid receptor. Subsequently, we have shown that opioid receptors are involved in ischemic preconditioning (PC) in the rat heart and that morphine produces a cardioprotective effect; however, the class of opioid receptors involved in mediating these effects is still unknown. Therefore, the purpose of the present study was to test the hypothesis that ischemia- and morphine-induced cardioprotection are mediated via stimulation of the delta-opioid receptor in the rat heart. Anesthetized, open-chest Wistar rats were subjected to one of six protocols. The control group was subjected to 30 min of occlusion and 2 h of reperfusion. Ischemic PC was elicited by three 5 min occlusion periods interspersed with 5 min of reperfusion. Morphine-induced cardioprotection was produced by three 5 min morphine infusions (100 microg/kg/infusion, i.v.) interspersed with a 5-min drug-free period. To determine if the delta-opioid receptor has a role in ischemic PC and morphine-induced cardioprotection, naltrindole (NTI), a selective delta-opioid receptor antagonist, was utilized. NTI (5 mg/kg, i.v.) was given 10 min prior to ischemic PC (NTI+PC) or morphine infusion (NTI+MOR). Also, NTI (5 mg/kg, i.v.) was given 10 min before the 30 min occlusion period in untreated rats. Infarct size (IS) as a percent of the area at risk (AAR) was determined by 2,3,5-triphenyltetrazolium chloride staining. Ischemic PC and morphine infusions resulted in similar reductions in IS/AAR from 51+/-4 to 11+/-3 and 15+/-4% (*P<0.05), respectively. NTI completely abolished the cardioprotective effect induced by ischemia and morphine. The results of the present study suggests a role of delta;-opioid receptors in ischemic PC or morphine-induced myocardial protection in the rat.

Topics: Animals; Cardiovascular Agents; Heart; Ischemic Preconditioning, Myocardial; Male; Morphine; Myocardial Infarction; Myocardium; Naltrexone; Narcotic Antagonists; Rats; Rats, Wistar; Receptors, Opioid, delta; Thiopental

Renal effects of water loading on urine flow rate (V) and concentration (Uosm) were studied in Wistar rats subjected to minor or extensive surgery, under different kinds and level of anesthesia. In the explanted kidney of chronically prepared rats, under light chloralose anesthesia, 1 h.i.v. hypotonic fluid load increased V of the experimental (left) kidney 11 fold while Uosm decreased from 1181 +/- 142 to 210 +/- 80 mosm kg/H2O. In the acutely exposed kidney, under Inactin anesthesia, V increased 5 fold and Uosm decreased from 785 +/- 170 to 204 +/- 57 mosm/kg H2O. In similar experiments under Nembutal anesthesia V increased 4 fold but the urine did not become hypotonic. After acute surgery under Inactin anesthesia water diuresis can be induced but urine concentration before water loading is impaired. Urine hypotonicity after water loading is not achieved in acute experiments under Nembutal--an unsuitable approach to studies of water diuresis. Thus, a transition from antidiuresis to urine dilution can best be accomplished in the chronic explanted kidney model under light anesthesia and without invasive surgery.

Topics: Anesthesia; Anesthetics; Animals; Diuresis; Kidney; Kidney Function Tests; Male; Pentobarbital; Rats; Rats, Wistar; Surgical Procedures, Operative; Thiopental; Water

Drug therapy is usually optimized by concentration measurement in patient serum. High-performance liquid chromatography (HPLC) is one of the most important analytical techniques used for therapeutic drug monitoring (TDM) of drugs for which no immunoassay kits are available. HPLC has been frequently used for screening purposes in toxicology, too. The Merck Tox Screening System (MTSS) has been developed for the identification of substances by a combination of gradient HPLC with diode-array detection and identification with a database system. For routine TDM an isocratic HPLC system is more suitable because of shorter analysis time, better reproducibility of retention index and better precision of results. Therefore we defined a set of methods in steps of 10% of the two MTSS eluents. Three examples are shown: Amiodarone, Indometacine and Thiopental. New applications to test for other substances can be transferred to an isocratic system after a complete MTSS gradient run.

Topics: Amiodarone; Chemical Precipitation; Chromatography, High Pressure Liquid; Drug Monitoring; Humans; Indomethacin; Orphenadrine; Promazine; Quality Control; Sensitivity and Specificity; Thiopental

Chronic surgical explantation of the left rat kidney out of the abdominal cavity under the flank skin enabled easy access to the organ and ipsilateral urine collection under light chloralose anesthesia without virtually any surgical intervention. The glomerular filtration rate, urine flow and osmolality, sodium excretion, and medullary tissue hypertonicity were similar in the explanted and in the contralateral kidney, whereas p-aminohippurate clearance was 14% lower. The function of the explanted kidney was also compared with that of the kidney acutely exposed in rats under thiobutabarbital anesthesia and rendered euvolemic by isoncotic albumin infusion. Again, in both preparations renal function was comparable except that over time urine osmolality remained stable in the former and fell from 1,385 +/- 195 to 835 +/- 167 mosmol/kgH2O (P < 0.02) in the latter, indicating deterioration of urine concentration. Laser-Doppler probes could be easily applied in the explanted kidney to measure cortical and medullary blood flow. The new experimental model offers some advantages, both over studies using conscious rats and over experiments involving deep anesthesia and acute surgery.

Topics: Anesthesia; Animals; Chloralose; Diuresis; Glomerular Filtration Rate; Histological Techniques; Hypotonic Solutions; Kidney; Male; Osmolar Concentration; p-Aminohippuric Acid; Rats; Rats, Wistar; Thiopental; Urine

Studies on the mechanisms underlying Na balance in anaesthetized rats are complicated by the fact that the most frequently used barbiturate anaesthetics attenuate or abolish this phenomenon. In the present study we show that a combination of nonbarbiturate anaesthetics: chloralose (140 mg/kg i.v.) and ketamine (30 mg/kg i.m. ), preserve the ability of rats to excrete intragastrically applied NaCl loads dose dependently. Thus rats anaesthetized with this regime excreted 86-102% of in- tragastrically applied NaCl whereas rats anaesthetized with thiobutabarbitone sodium (Inactin) excreted only 20-28%. We conclude that chloralose/ketamine anaesthesia is suitable for studies on Na balance mechanisms.

Topics: Anesthetics, Intravenous; Animals; Blood Pressure; Chloralose; Dose-Response Relationship, Drug; Eating; Ketamine; Male; Potassium; Rats; Rats, Wistar; Sodium Chloride; Thiopental

This study was undertaken to investigate the effects of a cyclo-oxygenase and a nitric oxide synthase (NOS) inhibitor on duodenal mucosal alkaline secretion (DMAS), motility and mucosal permeability in inactin-, urethane- and alpha-chloralose anaesthetized rats. Proximal duodenum was perfused with a 150 mM NaCl solution and DMAS was determined by back titration. Mucosal permeability was assessed by measuring blood to lumen clearance of 51Cr-EDTA and duodenal motility by measuring intraluminal pressure. Mean arterial blood pressure and mucosal permeability were significantly lower in urethane- than in inactin- or alpha-chloralose anaesthetized rats (urethane: 90 +/- 2 mm Hg and 0.15 +/- 0.02 mL min-1 100 g-1; inactin: 112 +/- 5 mm Hg and 0.62 +/- 0.15 mL min-1 100 g-1; alpha-chloralose: 111 +/- 4 mm Hg and 0.61 +/- 0.06 mL min-1 100 g-1, respectively). Basal (pre-drug) DMAS was significantly lower in urethane rats (6.2 +/- 1.0 mumol cm-1 h-1) than in alpha-chloralose (9.3 +/- 1.2 mumol cm-1 h-1), but not different from that in inactin-anaesthetized rats (7.5 +/- 0.8 mumol cm-1 h-1). No or very few spontaneous duodenal contractions occurred under the control (pre-drug) conditions in any group. All animals responded to the cyclo-oxygenase inhibitor indomethacin or the NOS inhibitor N-nitro-L-arginine-methyl-ester (L-NAME) with induction of duodenal motility and an increase in DMAS. The effect of indomethacin or L-NAME on mucosal permeability was similar in all anaesthetic groups except that L-NAME induced a transient increase in the inactin and alpha-chloralose groups but a sustained increase in urethane-anaesthetized animals. It is concluded that inactin- and alpha-chloralose anaesthetized rats do not differ regarding the studied basal values. Urethane-anaesthetized animals differed from rats given the other two anaesthetics in that basal mucosal permeability and mean arterial blood pressure were lower. Endogenous prostaglandins and NO contribute to the postoperative ileus and the low rate of DMAS also in urethane- and alpha-chloralose.

Topics: Anesthesia, General; Anesthetics, Intravenous; Animals; Chloralose; Cyclooxygenase Inhibitors; Duodenum; Enzyme Inhibitors; Gastrointestinal Motility; Hydrogen-Ion Concentration; Indomethacin; Intestinal Mucosa; Male; NG-Nitroarginine Methyl Ester; Nitric Oxide Synthase; Rats; Rats, Inbred Strains; Thiopental; Urethane

The purpose of our study was to analyze the effect of cicletanine on kidney function by using clearance and free flow micropuncture techniques in anesthetized rats. In the clearance experiments, cicletanine was tested at three different doses (15, 30 and 60 mg/kg i.v.). The drug dose-dependently increased urine flow, and urinary sodium and chloride excretion. Renal potassium excretion was also significantly enhanced. Cicletanine was as effective as hydrochlorothiazide regarding fractional renal sodium excretion. Mean arterial blood pressure fell after cicletanine at doses of 30 and 60 mg/kg, but at none of the three doses tested did cicletanine affect renal plasma flow and glomerular filtration rate. In this regard it differed from hydrochlorothiazide which was found to markedly decrease glomerular filtration rate at a dose of 10 mg/kg i.v. A coadministration of cicletanine (20 mg/kg i.v.) and hydrochlorothiazide, at a maximal effective dose (20 mg/kg i.v.), induced an additional diuretic and saluretic effect. By puncturing of late proximal, early and late distal nephron segments, an action of cicletanine (30 mg/kg i.v.) in the superficial distal tubule could be established. Thus, cicletanine shares with the thiazide diuretics its tubular site of action despite the disparity in chemical structure between these drugs.

Topics: Animals; Diuretics; Glomerular Filtration Rate; Hydrochlorothiazide; Kidney; Male; Pyridines; Rats; Rats, Sprague-Dawley; Thiopental

The endogenous vasodilator endothelium-derived nitric oxide (EDNO) contributes to the regulation of vascular tone and organ perfusion. It has been suggested that some volatile anesthetics may diminish the influence of EDNO and thereby decrease regional blood flow.. Radioactive microspheres were used to determine regional hemodynamics in rats. The authors tested the hypothesis that halothane inhibits EDNO and, therefore, should diminish the response to nitric oxide synthesis inhibition by NW-nitro-L-arginine methyl ester (L-NAME) compared with either conscious or barbiturate-anesthetized rats.. NW-nitro-L-arginine methyl ester decreased blood flow to the brain by 23% (P < 0.005) in conscious rats to a level similar to that seen with either anesthetic agent. In both conscious and barbiturate-anesthetized rats, L-NAME increased blood pressure (BP) by 24 +/- 2 (P < 0.001) and 20 +/- 1 (P < 0.001) mmHg and total peripheral resistance (TPR) by 132% (P < 0.001) and 105% (P < 0.001), respectively. In contrast, during halothane anesthesia, both the pressor response (only 7 +/- 1 mmHg) and the increase in TPR (only 22%) were greatly diminished (P < 0.001). NW-nitro-L-arginine methyl ester decreased cardiac output (CO) by 47% (P < 0.001) and heart rate (HR) by 28% (P < 0.001) in conscious rats. In barbiturate-anesthetized rats, L-NAME decreased CO by 38% (P < 0.005) and HR by 13% (P < 0.001). In halothane-anesthetized rats, L-NAME changed neither CO nor HR. Thus halothane anesthesia largely eliminated the systemic response to EDNO synthesis inhibition. In conscious rats, L-NAME decreased blood flow to the heart (30%) and kidneys (47%). In barbiturate-anesthetized rats, L-NAME did not alter blood flow to the heart but decreased renal blood flow by 35% (P < 0.005). In halothane-anesthetized rats, L-NAME did not alter blood flow to either the heart or the kidneys. Overall, halothane blunted or blocked the systemic and regional hemodynamic responses to EDNO synthesis inhibition seen in conscious and barbiturate-anesthetized rats.. Halothane anesthesia greatly diminished or eliminated all systemic and regional hemodynamic responses to L-NAME. These data indicate that halothane anesthesia inhibits EDNO-mediated regulation of systemic and organ hemodynamics.

Topics: Animals; Arginine; Cerebrovascular Circulation; Endothelium, Vascular; Halothane; Hemodynamics; Male; Microspheres; NG-Nitroarginine Methyl Ester; Nitric Oxide; Pulmonary Gas Exchange; Rats; Rats, Sprague-Dawley; Renal Circulation; Thiopental

The first part of this study evaluates a new paired microinjection technique for studying single-nephron permeability (in this case to calcium) following injection of 5-10 nL of a Ringer solution into a superficial proximal tubule. The mean difference in fractional 45Ca recovery from two identical microinjections into the same nephron site was 2.2 +/- 0.2% for 89 paired microinjections. Individual nephrons therefore normally show differences in calcium permeability with time. However, moment-to-moment variations in ion transport in any one nephron are in a random direction; differences cancel one another out if enough experiments are performed. The technique thus appears well suited to studies where comparisons are made between the acute nephron responses to two test solutions. It specifically overcomes problems of nephron heterogeneity seen in some other micropuncture techniques. The second part of this study uses the new technique to investigate the effects of a raised intratubular D-glucose concentration on single-nephron calcium transport. Urinary 45Ca recoveries from late proximal microinjections were significantly higher when D- (as opposed to L-) glucose was included in the injectate (6.87 +/- 0.88 vs. 5.24 +/- 0.50%; p < .02). The ability of D-glucose to depress tubular calcium reabsorption at distal nephron sites may contribute to the observed hypercalciuria following systemic D-glucose loading. It may also be relevant to the acute renal failure accompanying renal stone disease, where a relationship between hypercalciuria, urolithiasis, and the consumption of refined carbohydrates has been proposed.

Topics: Animals; Calcium; Calcium Radioisotopes; Cell Membrane Permeability; Drug Interactions; Glucose; Inulin; Isotonic Solutions; Male; Microinjections; Nephrons; Rats; Rats, Sprague-Dawley; Ringer's Solution; Thiopental; Time Factors; Tritium

Rilmenidine binds to alpha 2-adrenoceptors and imidazoline receptors in the central nervous system and the kidney. To test the hypothesis that rilmenidine would increase sodium excretion, renal function was studied in rats with innervated and denervated kidneys to distinguish between indirect (via renal sympathetic nerves) and direct effects of rilmenidine on the kidney. Standard clearance techniques were used in Wistar rats anesthetized with thiobutabarbital to measure renal function during 80 minutes of infusion of 0.9% NaCl or rilmenidine (20 or 50 micrograms.kg-1.min-1 intravenously). Snares on abdominal arteries were used to offset hypotension induced by rilmenidine. Heart rate decreased by 80-120 beats/min with either dose of rilmenidine. At 20 micrograms.kg-1.min-1, rilmenidine increased total and fractional excretion of sodium and clearance of osmoles while decreasing free water clearance from innervated kidneys. There were no changes in these variables in chronically denervated kidneys. Direct recording of renal sympathetic nerve activity showed a progressive, marked decrease in nerve activity during the low-dose infusion of rilmenidine. At 50 micrograms.kg-1.min-1, rilmenidine produced a differential effect on the clearance of osmoles by innervated and denervated kidneys but both kidneys had an increase in free water clearance. The data indicate that rilmenidine increases sodium excretion indirectly in anesthetized rats by decreasing renal sympathetic nerve activity. At doses and infusion periods used in these studies, there was no evidence for a direct effect of rilmenidine on sodium excretion. The increase in free water clearance seen with the high dose of rilmenidine suggests that the inhibitory effect of alpha 2-adrenoceptor activation on vasopressin is involved at this dose.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Adrenergic alpha-Agonists; Adrenergic Fibers; Animals; Hemodynamics; Kidney; Natriuresis; Oxazoles; Rats; Rats, Wistar; Rilmenidine; Sodium; Thiopental

We tested the hypothesis that proximal tubular Li+ reabsorption is due to passive transport. Clearances of [14C]inulin (CIn) and Li+ (CLi), proximal transepithelial electrical potential difference (PD), and tubular fluid-to-plasma Li+ concentration ratios [(TF/P)Li] were measured in anesthetized rats before and after induction of osmotic mannitol diuresis. Late proximal (TF/P)Li was measured after acute intravenous LiCl administration and after addition of LiCl to the diet for 2 days. Glomerular filtration rate (CIn) decreased, whereas CNa and CLi increased during osmotic diuresis. Control early proximal PD was -0.6 mV (lumen negative); late proximal PD (PDLP) was 1.1 mV (lumen positive). PDLP decreased by 1.5 mV to -0.4 mV (lumen negative) after mannitol infusion. Late proximal (TF/P)Li was 1.01 after oral Li+, 1.16 after intravenous Li+ (P < 0.01), and 1.00 during osmotic diuresis. It is concluded that proximal Li+ transfer is distinct from that of Na+, closely parallels proximal water transfer, and involves an active transport mechanism independent of the PD. The data suggest that acute elevation of plasma Li+ concentration may activate a delayed Li+ transport pathway in the proximal convoluted tubule.

Topics: Anesthesia; Animals; Biological Transport, Active; Diet; Diuresis; Electrochemistry; Halothane; Injections, Intravenous; Kidney Tubules, Proximal; Lithium; Male; Mannitol; Punctures; Rats; Rats, Inbred Strains; Thiopental

We introduce a rat model that allows simultaneous or independent recording of bladder and sphincteric activity. Via a polyethylene tube inserted into the bladder dome, bladder pressure is measured in response to constant intravesical saline perfusion. The electrical activity of the intra-abdominal urethra (a well-defined striated muscular tube which, in the rat, constitutes the external urethral sphincter) is recorded simultaneously with an electromyography needle electrode. Thus, precise statements can be made about detrusor/sphincter interrelationships. Changes in urodynamic parameters with the anesthetics urethane, methoxyflurane (Metofane), and thiobutabarbital sodium (Inactin) were investigated. High-frequency oscillations in intraluminal bladder pressure could be demonstrated during micturition cycles only in rats anesthetized with urethane or Metofane. As this high-frequency activity is generated by the striated muscle of the intra-abdominal urethra, the external sphincter of the rat is the force behind urine expulsion. The anesthetic Inactin combined with a low intravesical perfusion rate attenuated spontaneous bladder and sphincteric activity and abolished micturition cycles. This rat model can provide accurate and reproducible measurements of urodynamic changes in response to electrical stimulation of the pelvic and pudendal nerves and pharmacologic stimulation with neuropeptides at the lumbosacral spinal cord level. We recommend using this model with urethane or Metofane for physiologic studies of micturition and with Inactin for meticulous neuropharmacologic and electrostimulatory evaluation of urodynamic parameters.

Topics: Animals; Electric Stimulation; Electromyography; Lidocaine; Male; Methoxyflurane; Nervous System Physiological Phenomena; Pressure; Rats; Rats, Wistar; Stimulation, Chemical; Thiopental; Urethra; Urinary Bladder; Urination; Urodynamics

The thiobutabarbitone(TB, Inactin)-anaesthetised rat is an extremely widely used preparation for the study of renal function at the whole-organ and nephron levels. The recent withdrawal of TB from the market has made it essential to find an anaesthetic producing experimental conditions as similar as possible to TB to allow comparison of past and future data. Blood gas analysis, clearance and micropuncture studies were therefore performed in rats anaesthetised with TB or the related thiobarbiturate thiopentone (TP) (both 100 mg/kg body weight) to establish whether the latter meets this requirement. Both barbiturates caused similar transient respiratory depression and acidosis. Mean values (TP versus TB) over the total 8-h observation period for glomerular filtration rate (0.94 versus 1.05 ml/min), urine flow (3.8 versus 4.4 microliters/min) and K+ excretion (0.98 versus 1.18 mumol/min) were slightly lower (P < 0.05) in TP rats, whereas renal blood flow (6.26 versus 6.24 ml/min), filtration fraction (0.31 versus 0.34) and Na+ excretion (0.11 versus 0.098 mumol/min) did not differ. The single-nephron filtration rate (SNGFR) (42.1 versus 41.1 nl/min) and fractional reabsorption (42% versus 47%), both measured in the proximal tubule, did not differ, although in the TP group SNGFR rose with time (4.4%/h) whereas the fractional reabsorption did not change significantly; in the TB group SNGFR was constant but fractional reabsorption declined with time (1.5%/h). Fractional reabsorption up to the distal convoluted tubule declined with time, this was more pronounced in the TP group. SNGFR measured at this site did not differ between TP and TB (30.3 versus 30.1 nl/min) but increased with time with TP (2.7%/h).(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Acid-Base Equilibrium; Anesthesia; Animals; Blood Gas Analysis; Kidney; Kidney Glomerulus; Male; Nephrons; Rats; Rats, Wistar; Renal Circulation; Thiopental; Urodynamics

We investigated the cerebral blood flow (CBF) response to somatosensory stimulation. Stimulation of neuronal activity was performed by deflection (2-3/s) of the mystacial vibrissae in rats over a period of 60 s, and regional cortical CBF was measured continuously in the contralateral somatosensory cortex with laser-Doppler flowmetry. CBF within the somatosensory cortex was studied through the parietal bone thinned to translucency (n = 7) or through a closed cranial window with the dura mater removed (n = 7). In addition, the differential effect of anesthetics (halothane-N2O, n = 5; thiobutabarbiturate, n = 5; and alpha-chloralose, n = 7) on the CBF response to stimulation was investigated. After a rapid increase after stimulation onset (maximum reached within 2-3 s), CBF remained above baseline with a slight tendency to decrease despite continued stimulation. On termination of stimulation, CBF fell to near prestimulation values within 2-3 s. The following mean CBF responses above baseline during the 60-s stimulation period were obtained: halothane-N2O anesthesia, 25.4 +/- 5.9%; thiobutabarbiturate anesthesia, 10.6 +/- 2.4%; and alpha-chloralose anesthesia, 16.9 +/- 2.3 (through the translucent bone) and 16.2 +/- 2.9% (closed cranial window, dura removed). We conclude that coupling of CBF to neuronal function has a very high temporal resolution (< 3 s) and that whisker deflection in rats provides a physiological stimulus to study coupling with laser-Doppler flowmetry.

Topics: Anesthetics; Animals; Cerebral Cortex; Chloralose; Halothane; Lasers; Male; Neurons, Afferent; Rats; Rats, Wistar; Regional Blood Flow; Somatosensory Cortex; Thiopental; Vibrissae

This study was designed to test whether previous work, which showed that the angiotensin converting enzyme (ACE) inhibitor enalaprilat potentiated the alpha 1-adrenoceptor antagonist activity of doxazosin in isolated rat tail arteries, could be extended to demonstrate a synergistic hypotensive effect of these two drugs.. Groups of untreated or chronically deoxycorticosterone acetate (DOCA)-salt-treated female Sprague-Dawley rats were used. Rats were anaesthetized with Inactin (barbiturate); drugs were administered via a jugular venous catheter; blood pressure was monitored via a carotid arterial catheter.. In previously untreated rats, pretreatment with enalaprilat shifted the dose-response curve for the hypotensive effect of doxazosin to the left, indicating synergism. In rats dosed with DOCA-salt (which suppresses renin and angiotensin II production): (1) there was no synergism between the hypotensive actions of enalaprilat and doxazosin; (2) doxazosin was more potent than in untreated rats; and (3) enalaprilat lowered blood pressure, suggesting a hypotensive mechanism separate from ACE inhibition.. In the absence of angiotensin II (resulting from enalaprilat administration or from chronic DOCA-salt), doxazosin had a greater hypotensive action than in the presence of angiotensin II. This is consistent with the concept that angiotensin II modulates alpha 1-adrenoceptor activity.

Topics: Anesthesia; Animals; Antihypertensive Agents; Desoxycorticosterone; Disease Models, Animal; Dose-Response Relationship, Drug; Doxazosin; Drug Evaluation, Preclinical; Drug Interactions; Enalaprilat; Female; Hypertension; Prazosin; Rats; Rats, Inbred Strains; Thiopental

The influence of blood sampling, anesthesia and surgery on plasma vasopressin concentration was assessed in rats. Mean plasma concentration in conscious, chronically catheterized rats was 1.4 +/- 0.1 pg/ml (n = 6). This value remained constant over repeated plasma samplings in the same animals. On the other hand, decapitation increased the plasma vasopressin concentration to 6.0 +/- 2.4 (in pg/ml) (n = 6), inactin anesthesia to 2.9 +/- 0.6 (n = 6), anesthesia and femoral cannulation to 13.3 +/- 5.8 (n = 6) and surgery for renal micropuncture to 81.3 +/- 35.0 (n = 6). It is concluded that the level of circulating plasma vasopressin is highly dependent on the sampling technique and is closely related to the extent of surgery.

Topics: Anesthesia; Animals; Blood Specimen Collection; Bloodletting; Female; Kidney; Rats; Thiopental; Vasopressins

Few safe and effective anesthesia regimens have been described for use in rabbits, partially because of the susceptibility of this species to sometimes fatal respiratory depression. Although inhalant anesthetics are generally safer than injectable anesthetics, their use may be limited by lack of equipment or facilities. This study was conducted to compare effects of several injectable anesthetics in rabbits on response to noxious stimuli, heart rate, respiratory rate, and rectal temperature. Six injectable anesthetic combinations were administered to rabbits: xylazine-ethyl-(1-methyl-propyl) malonyl-thio-urea salt (EMTU), ketamine-EMTU, xylazine-pentobarbital, xylazine-acepromazine-ketamine (XAK), ketamine-chloral hydrate, and ketamine-xylazine. All combinations induced a depression of respiratory rate. Although rectal temperature values were reduced to some degree in each group, the most profound hypothermia was induced by XAK. The combination that induced the longest duration of anesthesia was XAK. It was concluded that XAK was preferable for longer periods of anesthesia (60 to 120 minutes), although it induces severe hypothermia. For short periods of anesthesia, xylazine-pentobarbital, xylazine-EMTU, or ketamine-xylazine were deemed adequate; however, xylazine-EMTU induced the best survivability and consistency.

Topics: Anesthesia; Anesthetics; Animals; Body Temperature; Chloral Hydrate; Drug Combinations; Female; Heart Rate; Injections, Intramuscular; Injections, Intravenous; Injections, Subcutaneous; Ketamine; Male; Pentobarbital; Rabbits; Respiration; Thiopental; Xylazine

Renal function was examined in unrestrained conscious rats maintained on either a control diet or a low-potassium diet, then re-examined in the same animals after thiobutabarbital (Inactin) anaesthesia and preparation for micropuncture studies. In conscious rats, insulin clearance (CIn) was not significantly different in the two groups (control 1012 +/- 43, low-K 904 +/- 58 microliters/min per 100g body wt; mean +/- SE), but lithium clearance (CLi; used as an estimate of end-proximal fluid delivery) and fractional lithium excretion (FELi) were substantially reduced in the low-K group (CLi: 246 +/- 11 vs 126 +/- 8 microliters/min per 100g body wt, P less than 0.001; FELi: 0.245 +/- 0.009 vs 0.143 +/- 0.008, P less than 0.001). Following anaesthesia and preparation for micropuncture, there were significant reductions in urine flow rate and sodium excretion in the control group, but not in the low-K rats. Potassium excretion increased in both groups, but values in the potassium-depleted animals remained extremely low. In neither group of rats was preparation for micropuncture associated with significant changes in CIn, CLi or FELi. Thus, differences in tubular function between control and potassium-depleted rats were still apparent. The results suggest that preparation for micropuncture disturbs the function of the distal nephron, but that rates of glomerular filtration and proximal tubular reabsorption remain similar to values in conscious animals.

Topics: Anesthesia; Animals; Blood Pressure; Glomerular Filtration Rate; Inulin; Kidney; Lithium; Male; Potassium; Rats; Sodium; Thiopental

Influence of drugs on the cessation time of the brain electrical activity (resistance time) during total cerebral ischaemia evoked by clamping of the aorta for 50 sec; on the duration of its reappearance during reperfusion (restitution time) and on the background activity of EEG were studied. The experiments were carried out in 7 groups. Each group contained 5 animals. Nine clampings with intermittent reperfusion periods of 10 min were performed in each animal. One group served as control. In the remaining ones after the first three clampings the animals were given Glyo-6, Nootropil, Verpamil, Epanutin, Inactin or Lidocain. The resistance and restitution times measured in the control group as well as the reproductibility of the power spectrum values of the EEG provided evidence for the stability of the model. Glyo-6 in a dose of 10 mg/kg, Nootropil in a dose of 100 mg/kg or Verpamil in a dose of 0.125 mg/kg did not alter the above-mentioned parameters. As an effect of the administration of Epanutin in a dose of 10 mg/kg, the resistance time increased slightly, whereas restitution time decreased significantly. Administration of Inactin in a dose of 15 mg/kg, or Lidocain in a dose of 100 mg/kg increased considerably resistance time for a period of about one hour. The results indicate that in the initial phase of ischaemic brain damage both the cessation of EEG activity and the restitution during reperfusion after short-term occlusion of the circulation can be influenced favourable with drugs which decrease cerebral metabolism, inhibit synaptic transmission and have membrane stabilizing effect.

Topics: Animals; Dogs; Electroencephalography; Ischemic Attack, Transient; Lidocaine; Phenytoin; Piracetam; Pyridoxine; Thiopental; Verapamil

1. The effects of acute unilateral renal denervation were examined in 17 anaesthetized rats. Renal haemodynamic changes were monitored using standard clearance techniques. Lithium clearance was used to assess fractional proximal sodium and water reabsorption. 2. Denervation resulted in ipsilateral renal vasodilatation with marked natriuresis and diuresis, a small increase (15%, P less than 0.05) in glomerular filtration rate (GFR) and a consequent reduction in filtration fraction. Fractional lithium reabsorption decreased (67.3 +/- 2.9% to 54.5 +/- 4.0%, P less than 0.01) and absolute proximal reabsorption did not change, indicating impairment of proximal glomerulotubular balance (GTB). No similar changes in haemodynamic or transport parameters were observed in the contralateral, innervated kidney, although vascular resistance increased. 3. In 9 experiments following denervation of the left kidney, systemic low dose infusion (10 ng/min) of atrial natriuretic factor (ANF) resulted in a fall in mean arterial blood pressure from 116 +/- 3 mmHg to 107 +/- 3 mmHg (P less than 0.05). In the denervated kidney ANF increased urine flow rate and sodium excretion to rates above those established following denervation alone. However, in the right kidney, despite the increased filtered load (35%, P less than 0.01), the natriuretic and diuretic responses to ANF were abolished. 4. In the denervated kidney, ANF further reduced the fractional reabsorption of lithium from 53.6 +/- 2.3% to 45.6 +/- 3.8% (P less than 0.05). GFR increased by 32% (a total of 49% higher than during pretreatment) but absolute proximal reabsorption (APR) did not change. However, in the right, innervated kidney ANF infusion produced a 35% increase in GFR accompanied by a 53% rise in APR. 5. It is concluded that the natriuresis induced by unilateral denervation is due predominantly to impaired proximal GTB. The natriuretic action of ANF was associated with further impairment of proximal GTB, not dependent upon decreasing activity of renal sympathetic nerves, but was abolished when filtration fraction and renal sympathetic tone were elevated.

Topics: Absorption; Animals; Atrial Natriuretic Factor; Denervation; Diuresis; Hemodynamics; Kidney; Kidney Tubules, Proximal; Lithium; Male; Metabolic Clearance Rate; Natriuresis; Rats; Rats, Inbred Strains; Thiopental

Due to the exceptionally long duration of action of thiobutbarbital the anaesthetic properties of this barbiturate was reinvestigated with an intravenous threshold technique using butabarbital and hexobarbital as references. Adult male rats were used. The criterion of anaesthesia was a burst suppression in the EEG of 1 sec. or more (the "silent second" = SS). The dose which induced the criterion was used as a threshold. The barbiturates were infused with different rates to obtain dose rate curves. After induction of the threshold criterion the animals were either killed and different tissue concentrations were analyzed with a HPLC method or allowed to survive and duration of SS and duration of loss of righting reflex were recorded. With hexobarbital, duration of SS and of loss of righting reflex increased significantly with increasing dose rate. With increasing rates of thiobutabarbital and butabarbital there was in both cases a stepwise increase in duration of SS. At sacrifice, after induction of SS with slow rates brain concentrations of both thiobutabarbital and butabarbital were lower than values recorded after higher rates. The change between the two concentrations was abrupt and occurred at a rate of 20 mg/kg/min. with thiobutabarbital and at the rate of 1.25 mg/kg/min. with butabarbital. This phenomenon was the reverse of acute tolerance which was recorded with hexobarbital and can thus be denoted acute supersensitivity. A kinetic analysis of serum, muscle and fat indicated considerable differences between the barbiturates. As indicated by mortality figures the induction of acute supersensitivity could be potentially dangerous.

Topics: Anesthetics; Animals; Barbiturates; Brain Chemistry; Electroencephalography; Hexobarbital; Infusions, Intravenous; Injections, Intravenous; Male; Rats; Rats, Inbred Strains; Thiopental

Renal function was assessed in unrestrained conscious rats during either their active period (i.e. the hours of darkness) or their inactive period. On the following day, measurements were repeated after Inactin anaesthesia and preparation for clearance studies. In rats anaesthetized during their active period, preparation for clearance studies had no effect on inulin clearance (used as a measure of glomerular filtration rate), lithium clearance (used as an estimate of end-proximal fluid delivery) or fractional lithium excretion. In rats anaesthetized during their inactive period, the same procedures resulted in increases in all three variables, to reach values indistinguishable from those in animals studied during their active period. In both groups of rats there were increases in the fractional reabsorption of sodium and water in the distal nephron and in the urinary excretion of potassium. It is concluded that in anaesthetized rats prepared for clearance studies, rates of glomerular filtration and proximal tubular reabsorption (as indicated by lithium clearance) are similar to those in conscious animals during their active period.

Topics: Absorption; Activity Cycles; Anesthesia; Animals; Body Water; Diuresis; Glomerular Filtration Rate; Inulin; Kidney; Lithium; Male; Natriuresis; Osmolar Concentration; Potassium; Rats; Sodium; Surgical Procedures, Operative; Thiopental; Urine

The effects of combined renin inhibition and converting enzyme inhibition on mean arterial pressure and the plasma renin-angiotensin system were studied in conscious rats. In sodium-replete rats the infusion of the renin inhibitor CP71362 (100 micrograms/kg/min) decreased blood pressure by 13 +/- 1 mm Hg (p less than 0.0001), reduced plasma renin activity to undetectable levels, but did not lower plasma angiotensin II. In rats treated chronically with enalapril (30 mg/kg/day), CP71362 decreased blood pressure by an additional 5 +/- 2 mm Hg (p less than 0.025) and reduced plasma renin activity and angiotensin II concentrations to undetectable levels. The effects of renin inhibition were also tested under conditions where the renin-angiotensin system was stimulated. In rats on a low sodium diet, CP71362 decreased blood pressure by 15 +/- 2 mm Hg (p less than 0.0001), a decrease similar to that in rats on a normal diet. Plasma renin activity was decreased below detectable limits, but plasma angiotensin II concentrations were not reduced. In rats on a low sodium diet treated chronically with enalapril, CP71362 did not further decrease blood pressure although angiotensin II levels were significantly reduced. An additive effect of combined converting enzyme and renin inhibition on blood pressure lowering and inhibition of plasma angiotensin II was found in rats anesthetized with Inactin.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Anesthesia; Angiotensin-Converting Enzyme Inhibitors; Animals; Blood Pressure; Consciousness; Diet; Diet, Sodium-Restricted; Male; Oligopeptides; Rats; Rats, Inbred Strains; Reference Values; Renin; Renin-Angiotensin System; Thiopental

Open-loop tubulo-glomerular feedback (TGF) responses were measured in halothane anaesthetized spontaneously hypertensive rats (SHR), in normotensive Wistar Kyoto (WKY) and Sprague-Dawley rats (SPRD), and in inactin anaesthetized SPRD. Proximal intratubular free flow pressures (FFP) (13.8-14.7 mm Hg) and stop-flow pressures (40.0-42.4 mm Hg) were similar in the four groups, but systemic arterial pressure was significantly lower in WKY, and significantly higher in SHR than in SPRD. The turning point (Tp) of the feedback curve was 9.87 nl/min in SHR, significantly lower than the 13.04 nl/min found in WKY. Maximum TGF pressure response was 28.6% greater in SHR than in the normotensive rats (13.3 vs. 9.5 mm Hg; p less than 0.025). The sensitivity, as estimated from the slope of the feedback curve at the Tp [f'(Tp)] was 87% greater in SHR than in WKY. There was no significant difference between these parameters in WKY and SPRD. The TGF pressure response was biphasic in the 3 groups of halothane anaesthetized rats with a steady state level reached in about 2 min after the change in late proximal microperfusion rate. In inactin anaesthetized rats the sensitivity was 41% lower than in the halothane anaesthetized control group of SPRD, the feedback response was lower, and the feedback curve was displaced to the right with the Tp at 15.9 nl/min, significantly higher than in the control group (p less than 0.001). Although the steady state level also was reached within 2 min, the clearly biphasic pattern of the pressure response was less consistent.

Topics: Animals; Blood Flow Velocity; Blood Pressure; Feedback; Halothane; Hypertension; Kidney Glomerulus; Kidney Tubules, Proximal; Male; Rats; Rats, Inbred SHR; Rats, Inbred Strains; Rats, Inbred WKY; Thiopental

The constancy of rat EEG during surgical anaesthesia induced by phenobarbital, cholorose, paraldehyde, and inactin was investigated. The results showed that intraindividual variations and spontaneity of EEG were not abolished in the anaestheized animals. However, at the higher of the two doses used, the EEG was less variable. Our findings thus indicate that in the study of drug actions on the EEG of anaesthetized animals, the results obtained not only represent the interaction of the anaesthetic and the drug on the animal EEG but is also a reflection of the dosage of the anaesthetic employed.

Topics: Anesthesia, General; Animals; Chloralose; Electroencephalography; Paraldehyde; Phenobarbital; Rats; Rats, Inbred Strains; Thiopental

To determine the mechanism by which immobilization and head-up tilt under inactin anesthesia increase plasma renin activity (PRA), the effect of these stimuli on plasma levels of vasoactive intestinal polypeptide (VIP) were measured and the effect of the beta-adrenergic blocking drug, propranolol on the response of plasma renin activity determined. Increases in circulating VIP are known to stimulate secretion of renin. After 10 min of immobilization, plasma renin activity was increased and VIP in plasma was unchanged. After 30 min of tilting, plasma renin activity was also increased and VIP in plasma was unchanged. The increases in plasma renin activity were blocked by propranolol. Inactin anesthesia by itself increased plasma renin activity and this response was unaffected by propranolol and associated with a small decrease, rather than an increase in VIP in plasma. The results indicate that the responses of plasma renin activity to immobilization and head-up tilt are due to increased secretion of renin mediated by the sympathetic nervous system. On the other hand, the increase in secretion of renin produced by inactin anesthesia does not appear to be mediated by the sympathetic nervous system. There was no evidence that VIP was responsible for any of the increases.

Topics: Animals; Immobilization; Infusions, Intravenous; Injections, Intraperitoneal; Male; Orientation; Propranolol; Rats; Rats, Inbred Strains; Renin; Sympathetic Nervous System; Thiopental; Vasoactive Intestinal Peptide

The effects of pentobarbital (30 mg/kg), urethan (2 g/kg), chloralose/urethan (50 mg/kg, 500 mg/kg), and thiobutabarbital (Inactin, 100 mg/kg) on the mean arterial pressure (BP) and heart period (HP) of Marmota flaviventris were examined. Anesthesia significantly decreased BP by 22-27 mm Hg and HP by 123-151 msec. In a series of paired studies with eight marmots it was found that pentobarbital increased the BP response to phenylephrine and almost abolished the baroreflex HP responses to phenylephrine and nitroglycerin. In another series of animals right carotid occlusion in unanesthetized animals produced greater changes in BP and HP than occlusion of the left carotid. Chloralose/urethan, urethan, or Inactin reduced the reflex BP response to unilateral carotid occlusion by 50% and the HP response by 96%. It was concluded that the anesthetic agents investigated depress baroreflex responses significantly by influencing efferent sympathetic and parasympathetic reflex responses. They, therefore, are not appropriate for cardiovascular studies in acute, anesthetized preparations of the marmot and, perhaps, other hibernating species.

Topics: Anesthetics; Animals; Blood Pressure; Cardiac Output; Chloralose; Dose-Response Relationship, Drug; Heart Rate; Marmota; Nitroglycerin; Pentobarbital; Phenylephrine; Reference Values; Sciuridae; Species Specificity; Thiopental; Urethane

In rats anesthetized with ketamine and pentobarbital (KET/PB), vasoactive intestinal peptide (VIP) increases vascular conductance (VC) in the salivary gland, pancreas, and thyroid gland, whereas no changes in VC are observed in a number of other organs. Because anesthesia may alter the responsiveness of physiological systems, we compared the effects of VIP on organ VC in conscious or anesthetized rats. Chronically catheterized rats were studied in the conscious state or 30 min after induction of anesthesia with KET/PB, isoflurane, or Inactin. Blood flows were measured by the reference sample version of the radioactive microsphere (MS) technique using two MS injections (141Ce-MS/85Sr-MS). Mean arterial blood pressure was monitored and used in the calculation of VC. Organ VCs were similar under basal conditions in conscious and anesthetized rats. VIP infusion caused systemic hypotension and increased VCs in the salivary gland, pancreas, and thyroid gland, and these responses were largely unaffected by anesthesia. These results indicate that the anesthetics used do not alter basal VC or the responsiveness of the vasculature to exogenous VIP.

Topics: Anesthesia; Animals; Isoflurane; Ketamine; Male; Microspheres; Pentobarbital; Rats; Rats, Inbred Strains; Regional Blood Flow; Thiopental; Vasoactive Intestinal Peptide

Experiments were designed to investigate further the alterations in calcium metabolism caused by inaktin, a thiobarbiturate that impairs parathyroid hormone action in rats (1981). Treatment with an anesthetic dose of inaktin induced a drop in serum calcium without any variation in immunoreactive parathyroid hormone serum level and slowed body calcium turnover as studied with 45Ca, but was without effect on blood pH or partial pressures of oxygen and carbon dioxide. In contrast, calcium metabolism in rats was unchanged after treatment with an anesthetic dose of pentothal, another thiobarbiturate anesthetic. The effect of inaktin on body calcium turnover was dose-dependent and significant even at non-anesthetic levels. A marked slowing of the fast phenomena accounting for the initial dilution of the tracer in the animal was observed, accompanied by a corresponding decrease in rapid 45Ca uptake into bone, but not other tissues. These results show that inaktin slows calcium turnover, especially the fast renewal of calcium in bone. These effects were not correlated with anesthesia or immobilization, and we suggest that inaktin-induced changes in calcium metabolism involve an impairment of hypocalcemia-induced parathyroid hormone secretion, in addition to the impairment of parathyroid hormone effects previously reported. Furthermore, the present findings suggest that inaktin might be a useful tool for investigation of the rapid mobilization of bone calcium, which is as yet not well understood.

Topics: Anesthesia, General; Animals; Calcium; Immobilization; Male; Parathyroid Hormone; Rats; Rats, Inbred Strains; Thiobarbiturates; Thiopental

A suicide is reported that was carried out by i.v. infusion of thiobutabarbital. The most impressive findings were macroscopical alterations in the venous endothelium, the endocardium of the right atrium and ventricle, and the endothelium of the pulmonary artery. The same local cytotoxic side effects could be reproduced in animal experiments. The lesions are most striking after circulatory stagnation in the agonal and supravital period when highly concentrated thiobarbiturates come into contact with the endothelium.

Topics: Adult; Animals; Endocardium; Endothelium, Vascular; Humans; Infusions, Intravenous; Male; Rats; Rats, Inbred Strains; Suicide; Thiopental; Veins

Rat tail artery segments were cannulated both ends, immersed in an organ bath filled with Krebs solution, and perfused at a constant 3 ml/min with Krebs solution from a reservoir or arterial blood from a donor conscious rat. Donor rats had chronic indwelling exteriorized silastic cannulas in a carotid artery and jugular vein. Blood withdrawn from the carotid artery returned to the donor rat via the jugular vein cannula after perfusing the tail artery segment. Arteries were constricted and perfusion pressure increased by infusing noradrenaline into the perfusate. In Krebs perfused arteries vasodilator responses were obtained to acetylcholine (ACh) and sodium nitroprusside (NP) infused for 1 min at 10(-6) M. The addition of the barbiturates, 'Inactin' (5-ethyl-5-(1-methylpropyl)-2-thiobarbiturate) and pentobarbitone, at 10, 30 and 100 micrograms/ml progressively inhibited responses to ACh but not to NP. Pentobarbitone 30 micrograms/ml also significantly inhibited responses to 3 X 10(-7) M of the calcium ionophore A23187, shifted the dose-response curve for ACh to the right and suppressed the maximum ACh response. Vasoconstrictor responses were also obtained by periarterial stimulation of the sympathetic nerves at 5 Hz for 5 s every 2 min. These responses were markedly inhibited by ACh (10(-5) M) and this inhibition was not affected by Inactin 100 micrograms/ml. In arterial segments perfused with blood from a donor conscious rat, ACh infused for 1 min at a rate calculated to produce a concentration of 10(-4) M in the blood perfusate at the site of infusion, decreased tail artery perfusion pressure.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Acetylcholine; Animals; Arteries; Barbiturates; Electric Stimulation; Endothelium; In Vitro Techniques; Male; Perfusion; Rats; Rats, Inbred Strains; Regional Blood Flow; Sympathetic Nervous System; Tail; Thiopental; Vasodilation

Cardiovascular disorders during endoscopy of the upper respiratory tract have since long induced anaesthetists and laryngologists to find a suitable anaesthetic procedure. It was the purpose of the present study to determine the influence exerted by different kinds of premedication and different modes of anaesthesia on the cardiovascular system, pO2, and the acid-base status. The results obtained show that a hypertensive-tachycardiac response to direct laryngo-tracheoscopy could not be prevented in any of the groups under investigation. Lowest blood pressure and heart rate increases were seen in those groups of patients which received an analgetic drug (Fentanyl or nitrous oxide) in addition to hexobarbital. During endoscopy, respiratory acidosis occurred in five groups of patients. All patients were sufficiently oxygenated.

Topics: Acid-Base Equilibrium; Adult; Anesthesia, General; Atropine; Blood Pressure; Bronchoscopy; Electrocardiography; Heart Rate; Hexobarbital; Humans; Laryngoscopy; Middle Aged; Oxygen; Preanesthetic Medication; Respiratory Tract Diseases; Succinylcholine; Thiopental

The relationship between urine flow and urinary prostaglandin E (PGE) excretion was investigated at constant urine pH in the anaesthetized rat. The urine pH was maintained at approximately pH 6 or pH 8 by the intravenous infusion of either ammonium chloride or sodium bicarbonate respectively. Two distinct patterns in the relationship between PGE excretion and urine flow were observed. The first showed a fall in urinary PGE excretion as the urine flow increased over the low flow range of 2-5 ml/h, and was common to both experiments. The second relationship, however, showed a marked difference between the ammonium chloride and sodium bicarbonate experiments since: (a) in acidic urine (pH 6), PGE excretion increased (P less than 0.002) with the urine flow, attaining a rate of 87 +/- 6 pmol/h (n = 6) at the highest level of flow achieved (12 ml/h); (b) in alkaline urine (pH 8), PGE excretion was significantly (P less than 0.01) higher but did not increase with urine flow, remaining constant at approximately 90 pmol/h (n = 6). The lack of any additive effect on urinary PGE excretion between increasing the urine flow and making the urine alkaline may be explained by both stimuli acting through a common mechanism, a concept which is consistent with the hypothesis that PGE may be reabsorbed in the distal nephron. The flow-dependency of urinary PGE excretion could therefore result from a reduction in reabsorption rather than the increase in passive secretion proposed previously.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Animals; Female; Hydrogen-Ion Concentration; Prostaglandins E; Rats; Rats, Inbred Strains; Thiopental; Urination

Proximal tubular compliance (C) was measured in free flow microperfusion experiments from the initial slope of the increase in proximal luminal pressure divided by the step input of volume flow delivered from a microperfusion pipette inserted in a downstream proximal convolution. Five groups of rats were studied: Munich Wistar (WU, n = 11) and Sprague-Dawley rats (SPRD, n = 6) anaesthetized with inactin; and SPRD (n = 11), Wistar Kyoto (WKY, n = 9), and spontaneously hypertensive rats (SHR, n = 11) anaesthetized with halothane. In the inactin groups, C was: 0.309 +/- 0.161 and 0.266 +/- 0.136 nl mm Hg-1, respectively. In the halothane groups, C was: 0.125 +/- 0.023, 0.125 +/- 0.029, and 0.119 +/- 0.0127 nl mm Hg-1, respectively. The means in the inactin groups were significantly higher than those from the halothane groups (P less than 0.001). It is concluded that the choice of anaesthetics has a profound influence on the proximal tubular compliance in the rat, and that the compliance of SHR is equal to that of normotensive rats.

Topics: Anesthesia, Inhalation; Animals; Compliance; Halothane; Hypertension; Kidney Tubules, Proximal; Male; Nitrous Oxide; Perfusion; Pressure; Rats; Rats, Inbred SHR; Rats, Inbred Strains; Rats, Inbred WKY; Thiopental

In order to analyse opiate receptors mediating anti-nociception, the activity pattern of different opiates was determined by using hot-plate (45 degrees C and 56 degrees C), tail-flick and algolytic tests on rats, and the acetic acid stretching test on mice, for evaluation of analgesic activity. Potentiation of barbiturate anaesthesia, measurement of pupillary diameter, and a modification of pentetrazol convulsion, were used for evaluation of non-analgesic activity. The efficacy and affinity constant (pA2) of the proposed opiate A receptor agonist and B receptor antagonist drug N-cyclopropylmethyl-norazido-dihydroisomorphine (CAM) were determined. CAM produced several opiate agonist (morphine-like) effects, often stronger than morphine, in three of the analgesic tests and two of the non-analgesic tests. On the other hand CAM proved to be a very strong narcotic antagonist, as potent as naloxone as evidenced by identical pA2 values, in the algolytic, 45 degrees C hot-plate and pentetrazol tests, but not in the 56 degrees C hot-plate, tail-flick and acetic acid tests. The potency differences for the actions of morphine and CAM in a heat test (56 degrees C hot-plate) compared with a non-heat test (acetic acid stretching) were found to be 8.6 and 540 respectively. It is concluded that opiate analgesia might be mediated by at least two receptors classified in terms of the antagonistic or agonistic activity of CAM.

Topics: Analgesics, Opioid; Animals; Dose-Response Relationship, Drug; Female; Lethal Dose 50; Male; Mice; Morphinans; Morphine; Nalorphine; Narcotic Antagonists; Oxymorphone; Pentazocine; Rats; Receptors, Opioid; Thiopental

The effects of synthetic human atrial 28-amino acid peptide (alpha-human atrial polypeptide) on systemic and renal hemodynamics were examined in two separate groups of Inactin-anesthetized rats. First, mean arterial pressure, heart rate, and cardiac output were measured before and during infusion of the peptide at rates of 0.04-0.67 microgram/kg per min. Cardiac output was determined by the dye-dilution method with a microcuvette inserted into a carotid-femoral arterial shunt. After 10 minutes of infusion, mean arterial pressure, cardiac output, and total peripheral resistance were reduced in a dose-dependent manner by 21% (P less than 0.001), 9% (P less than 0.05), and 11% (P less than 0.05), respectively, with 0.67 microgram/kg per min of alpha-human atrial natriuretic polypeptide. Despite the marked fall in blood pressure, the heart rate did not change. Second, urine volume, urinary sodium excretion, glomerular filtration rate ([3H]inulin clearance) and renal blood flow ([14C]p-aminohippuric acid sodium clearance and hematocrit) were measured. Increases in urine volume, urinary sodium excretion, filtration fraction, and fractional sodium excretion and a decrease in renal vascular resistance were dose dependent: +490% (P less than 0.01), +1340% (P less than 0.01), +19% (P less than 0.05), +1160% (P less than 0.01), and -18% (P less than 0.05), respectively, with 0.67 microgram/kg per min of alpha-human atrial natriuretic polypeptide. The glomerular filtration rate increased with 0.33 and 0.67 microgram/kg per min of alpha-human atrial natriuretic polypeptide (both P less than 0.05), whereas renal blood flow did not change.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Anesthesia; Animals; Atrial Natriuretic Factor; Blood Pressure; Cardiac Output; Diuresis; Glomerular Filtration Rate; Heart Rate; Hemodynamics; Kidney; Kinetics; Male; Natriuresis; Rats; Rats, Inbred Strains; Renal Circulation; Thiopental

Topics: Anesthesia; Animals; Body Water; Female; Kidney; Phenobarbital; Potassium; Rats; Sodium; Sodium Chloride; Thiopental

The effects of nine intravenous anaesthetic techniques on serum cortisol level and circulatory parameters were studied in healthy patients undergoing termination of pregnancy. Considering the increased pre-operation values and those of the pregnant control group as well as diurnal variations, it was found that the serum cortisol value changed during and after the procedure depending on the type of anaesthesia used. This might mean that the optimal type of anaesthesia for interruption could be designed by measuring the serum cortisol level, assuming that this parameter was one of the indicators of stress. The rating the different types of anaesthetics, the circulatory parameters were also considered. According to these criteria the best results were observed using methohexital in combination with fentanyl or diazepam.

Topics: Abortion, Legal; Adult; Anesthesia, Intravenous; Anesthesia, Obstetrical; Anesthetics; Blood Pressure; Diazepam; Drug Combinations; Female; Fentanyl; Humans; Hydrocortisone; Methohexital; Pregnancy; Pregnancy Trimester, First; Propanidid; Pulse; Thiopental

Renal electrolyte excretion has been examined in water loaded ethanol anaesthetised rats receiving continuous iv saline (0.077 M NaCl) infusion. These animals exhibited very low rates of Na+, K+ and Cl- excretion by comparison with Inactin anaesthetised rats. Water loaded Inactin anaesthetised rats also showed a degree of Na retention but both Na+ and K+ excretory rates were higher than in ethanol anaesthetised animals. Plasma aldosterone levels did not differ between ethanol and Inactin anaesthetised groups. Vasopressin administration did not effect Na+ but potentiated K+ excretion in ethanol anaesthetised animals. This contrasted with the potent natriuretic and weak kaliuretic action of vasopressin in water loaded Inactin anaesthetised rats. The significance of abnormal renal electrolyte handling and the marked kaliuretic effect of vasopressin to the use of ethanol anaesthetised animals for vasopressin bioassay is discussed.

Topics: Aldosterone; Anesthesia, General; Animals; Arginine Vasopressin; Diuresis; Ethanol; Kidney; Male; Potassium; Rats; Rats, Inbred Strains; Sodium; Sodium Chloride; Thiopental; Water; Water-Electrolyte Balance

Topics: Anesthesia, Intravenous; Animals; Animals, Laboratory; Swine; Swine, Miniature; Thiopental

Infant and small children are not always able to cooperate in impedance measurements. For this reason it was decided, -in special cases, -to perform acoustic reflex examination under general anaesthesia. The first report on stapedius reflex and general anaesthesia was published by Mink et al. in 1981. Under the effect of Tiobutabarbital, Propanidid and Diazepam there is no reflex response. Acoustic reflex can be elicited with Ketamin-hydrochlorid and Alphaxalone-alphadolone acetate narcosis. The reflex threshold remains unchanged and the amplitude of muscle contraction is somewhat increased. The method was used: 1. to assess the type and degree of hearing loss in children with cleft palate and/or lip prior to surgery. 2. to exclude neuromuscular disorders with indication of pharyngoplasties. 3. to quantify hearing level in children--mostly multiply handicapped--with retarded speech development. The results of Behavioral Observation and Impedance Audiometry are discussed and evaluated.

Topics: Acoustic Impedance Tests; Alfaxalone Alfadolone Mixture; Anesthesia, General; Diazepam; Humans; Ketamine; Propanidid; Reflex, Acoustic; Thiopental

Topics: Abortion, Induced; Chromatography, Gas; Decidua; Embryo, Mammalian; Female; Fetal Blood; Humans; Placenta; Pregnancy; Thiopental; Tissue Distribution

The transepithelial voltage (psi ms) of rat rectum in vivo increases for several hours in experiments under general anaesthesia. So far this was attributed by indirect evidence to increasing aldosterone plasma levels during the course of the experiment. We performed direct measurements of aldosterone and corticosterone plasma concentrations during intestinal perfusion experiments on barbiturate anaesthetized rats. Experiments were terminated for blood sampling at 10, 75, 300, 400, 800, or 1,800 min, respectively. (i) After 75 min of anaesthesia, surgical preparation was finished and plasma levels of aldosterone and of corticosterone were found increased by the factors 5 and 3, respectively, as compared to conscious controls. (ii) During the following 12 h, aldosterone further increased to levels 10 times as high as those of controls. In contrast, during the same period corticosterone slowly decreased but still remained elevated as compared to controls. (iii) The increase of both hormones was attenuated when abdominal surgery was omitted. (iv) The use of pentobarbital (Nembutal) instead of thiobarbital (Inactin) did not influence the adrenal response. (v) In adrenalectomized rats a continuous substitution with 65 ng X h-1 X kg-1 BWT aldosterone resulted in plasma levels as high as in conscious intact animals. (vi) Rectal psi ms started to move to higher lumen-negative values with a time delay of 1-1 1/2 h as compared with the increase of hormone levels. psi ms then stayed elevated until to the end of the experiments. We conclude that in vivo experiments of several hours duration in thio- or pentobarbital anaesthetized rats take place under conditions of aldosterone and corticosterone plasma levels which are high as compared to those of conscious unstressed animals.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Abdomen; Adrenalectomy; Aldosterone; Anesthesia, Intravenous; Animals; Corticosterone; Electrophysiology; Epithelium; Intestine, Large; Male; Pentobarbital; Perfusion; Rats; Rats, Inbred Strains; Thiopental; Thoracic Surgery

Topics: Anesthesia, Obstetrical; Cesarean Section; Chromatography, Gas; Female; Humans; Infant, Newborn; Placenta; Pregnancy; Thiopental

Real function, plasma renin concentration (PRC) and prostaglandin (PG) excretion rate was studied in groups of Sprague-Dawley (SPRD) and Wistar (WIST) rats anesthetized with either Halothane-N2O or Inactin. Conscious rats were used as controls. A. In Halothane-N2O anesthesia inulin clearance (CIN) and absolute proximal reabsorption rate (APR) was moderately decreased (by about 20%), while renal plasma flow (RPF), urine flow and solute excretion remained unchanged as compared to conscious rats. There was a linear relationship between the reciprocal of the proximal occlusion time (OT) and CIN in Halothane anesthesia indicating that the proximal luminal diameter was constant and independent of CIN. B. Inactin anesthesia CIN was similarly reduced but APR was more depressed (by about 35%). RPF and solute excretion rate decreased only in SPRD rats, while urine flow was significantly reduced in both strains. 1/OT was invariant to changes in CIN indicating luminal diameter variations in proportion to CIN. Urinary PGE2-and PGF2 alpha excretion rates and PRC were moderately elevated in operated animals of both strains regardless of the anesthetics used. It is concluded that renal functional parameters in surgically prepared rats are more severely depressed by Inactin than by Halothane-N2O anesthesia. The gas anesthesia is equally well tolerated by both strains of rats.

Topics: Anesthesia, Inhalation; Animals; Glomerular Filtration Rate; Halothane; Kidney; Kidney Tubules, Proximal; Nitrous Oxide; Prostaglandins E; Prostaglandins F; Rats; Rats, Inbred Strains; Regional Blood Flow; Renin; Thiopental

Renal and systemic adrenergic system responses were examined and compared under conditions of Inactin, a barbiturate, and alpha-chloralose anesthesia in hydropenic Munich-Wistar rats. Base-line plasma norepinephrine and other catecholamine levels were higher in Inactin-anesthetized rats. Norepinephrine was infused to raise blood pressure 15-20 mmHg above base line and plasma norepinephrine was again significantly higher with Inactin. In another group, angiotensin II was infused into the cerebral lateral ventricle in both Inactin- and alpha-chloralose-anesthetized rats, a method of stimulating centrally activated adrenergic output. After central stimulation, mean arterial pressure increased only in alpha-chloralose-anesthetized rats. Micropuncture studies examining systemic and glomerular hemodynamics were performed in alpha-chloralose- and Inactin-anesthetized rats before and after the infusion of phentolamine, an alpha-adrenergic antagonist. Infusion of phentolamine decreased mean arterial pressure to a significantly greater extent in the Inactin-anesthetized rats, suggesting a greater base-line systemic alpha-adrenergic activity with Inactin anesthesia. However, renal afferent and efferent arteriolar resistances were not significantly different after phentolamine, and any trend for resistances to decrease could be explained by autoregulation. Inactin increases systemic adrenergic activity, but renal vascular resistances are not significantly affected by this increased activity.

Topics: Anesthetics; Animals; Blood Pressure; Chloralose; Glomerular Filtration Rate; Kidney; Mathematics; Norepinephrine; Rats; Receptors, Adrenergic; Regional Blood Flow; Thiopental

Topics: Acute Kidney Injury; Animals; Humans; Ischemia; Kidney; Kidney Tubules, Proximal; Pentobarbital; Rats; Renal Artery Obstruction; Thiopental

Topics: Acute Kidney Injury; Animals; Ischemia; Kidney; Kidney Tubules, Proximal; Male; Pentobarbital; Polyuria; Rats; Renal Artery Obstruction; Thiopental; Urination

The mechanism by which inaktin, a thiobarbiturate, promotes a moderate drop in serum calcium has been investigated. The effect was cancelled in hypocalcemic parathyroidectomized rats. On the other hand inaktin antagonized the serum calcium raising effects of parathyroid extract in these animals. In rats wit intact parathyroid glands inaktin caused a two-fold increase in urinary calcium excretion and a marked decrease in body and bone calcium turnover (measured with 45 Ca). These results support the view that inaktin impairs the parathyroid hormone effects on calcium metabolism.

Topics: Anesthetics; Animals; Calcium; Male; Parathyroid Glands; Parathyroid Hormone; Rats; Rats, Inbred Strains; Thiopental

The investigations were carried out on 120 healthy pigs, aged from 3 to 7 months, weighing from 40 to 70 kg. The pigs were divided into 5 groups, 12 animals in each;, according to the agents administered intravenously. A similar arrangement of groups was adopted to determine the degree of bromsulphalein retention. Group I served as control. Blood was collected from the anterior vena cava after 1 hour and 1, 3 and 7 days since the moment of administration of physiological solution (group I) or since the appearance of general anaesthesia (groups II-V). The following determinations were made in serum: content of total protein and protein fractions; activity of AspAT, AlAT and ALD; bilirubin and retention of bromsulphalein; content of glucose in blood. The results were analysed statistically by determining the mean, the standard deviation and the test of significance t Student. The investigations resulted in the following conclusions. Anaesthesia produced in healthy pigs by the 4 preparations leads to considerable functional disturbances in the liver, expressed by increased activity of AspAT, AlAt and ALD, decreased albumin content, increased content of gamma globulins, and increased retention of bromsulphalein. The greatest changes were observed after chloral hydrate and Nembutal. After Eunarcon, the changes were fairly high, but of short duration. The slightest and most transient disturbances were found after Brevinarcon. These results make it possible to conclude that the functional disturbances of the liver after general anaesthesia are due to anoxia of this organ. In the present experiment, such disturbances were reversible, i.e. they receded after 7 days.

Topics: Anesthesia, Intravenous; Anesthetics; Animals; Barbiturates; Chloral Hydrate; Female; Injections, Intravenous; Liver; Male; Pentobarbital; Swine; Thiopental

1. The effect of sodium pentobarbital and Inactin anaesthesia on renal haemodynamics in the rat was evaluated with radioactive microspheres 15 micrometer in diameter. 2. Both anaesthetic agents caused substantial decrements in total renal blood flow (sodium pentobarbital, -34%; Inactin, -24%) compared with unanaesthetized animals. 3. Measurements of renal function obtained in rats anaesthetized with either of these anaesthetic agents should be interpreted with caution.

Topics: Anesthesia, General; Animals; Female; Kidney; Pentobarbital; Rats; Regional Blood Flow; Thiopental

Rats were anesthetized with pentobarbital, pentobarbital and atropine, inactin [5-ethyl-5-(1'-methyl-propyl)-2-thiobarbiturate], ether and inactin, or urethane. Cardiovascular and arterial acid-base parameters were monitored over a 3-hour period of anesthesia. Heart rate, arterial pressures, and pH progressively decreased with duration of pentobarbital anesthesia. Changes observed in rats anesthetized with the thiobarbiturate, inactin, were similar although generally less severe. Most subjects treated with the barbiturates were markedly hypercapnic. Urethane anesthesia was characterized by a higher and more stable heart rate and greater pulse pressure. Arterial carbon dioxide and bicarbonate levels in the urethane group were substantially lower at all sampling times than the values obtained in the barbiturate groups.

Topics: Acid-Base Equilibrium; Anesthesia, General; Animals; Atropine; Blood Pressure; Ether; Female; Heart Rate; Pentobarbital; Rats; Thiobarbiturates; Thiopental; Urethane

For decapitation of rats in order to determine brain acetylcholine (Ach) content the animals may be anaesthesized slightly by ether no longer than for 2 min, since forebrain Ach content increases quickly up to about 170% throughout the following 3 min. The progress of brain Ach content up to its maximum level is decided both by duration and degree of cns depression: In the moment of most distinctly marked Brevinarcon -narcosis -- evident 2,5 min after i. v. injection (40 mg/kg) -- the forebrain Ach content merely is increased by about 15%, but when anaesthesia is reduced considerably again -- 2,5 min later -- the Ach content only reaches its maximum level.

Topics: Acetylcholine; Anesthesia, General; Animals; Brain; Ether; Ethyl Ethers; Kinetics; Male; Rats; Thiobarbiturates; Thiopental

Adult, male hamsters anesthetized with lnactin [5-ethyl-5-(1-methyl propyl)-2-thiobarbiturate] were found to be hyperglycemic. Blood glucose concentrations in anesthetized hamsters (300.1+/-15.6 mg/dl) were more than twice those of control animals (144.8+/-7.7 mg/dl). Neither the length of time under anesthesia nor the performance of surgery influenced the blood glucose concentration.

Topics: Anesthesia; Animals; Blood Glucose; Cricetinae; Hyperglycemia; Male; Rodent Diseases; Thiobarbiturates; Thiopental; Time Factors

Topics: Barbiturates; Blood Circulation; Blood Pressure; Iodine Isotopes; Myocardium; Rabbits; Radiometry; Research; Thiopental; Toxicology

Topics: Anesthesia; Barbiturates; Blood Pressure; Cardiac Surgical Procedures; Heart Defects, Congenital; Heart Rate; Humans; Thiopental; Thoracic Surgery

Topics: Analgesia; Anesthesia; Anesthesia, Inhalation; Barbiturates; Minor Surgical Procedures; Thiopental; Trichloroethylene

Topics: Barbiturates; Chemistry, Pharmaceutical; Chromatography; Microchemistry; Research; Thiobarbiturates; Thiopental

Topics: Analgesia; Anesthesia; Anesthesia and Analgesia; Anesthesia, Intravenous; Anesthetics, Intravenous; Thiopental

Topics: Analgesia; Anesthesia; Anesthesia and Analgesia; Barbiturates; Thiopental

Topics: Analgesia; Anesthesia; Anesthesia and Analgesia; Barbiturates; Female; Genitalia; Genitalia, Female; Gynecologic Surgical Procedures; Gynecology; Humans; Thiopental

Topics: Barbiturates; Thiopental

Topics: Analgesia; Anesthesia; Anesthesia and Analgesia; Barbiturates; Ether; Thiopental

Topics: Analgesia; Anesthesia; Anesthesia and Analgesia; Barbiturates; Convulsive Therapy; Electroconvulsive Therapy; Humans; Narcotics; Psychiatry; Succinylcholine; Thiopental

Topics: Barbiturates; Thiobarbiturates; Thiopental

Topics: Analgesia; Anesthesia; Anesthesia and Analgesia; Barbiturates; Bronchography; Succinylcholine; Thiopental

Topics: Analgesia; Anesthesia; Anesthesia and Analgesia; Barbiturates; Guaifenesin; Muscle Relaxants, Central; Thiopental

Topics: Anesthesia; Anesthesiology; Hexobarbital; Humans; Reflex; Steroids; Thiopental

Topics: Analgesia; Anesthesia; Anesthesia and Analgesia; Barbiturates; Thiobarbiturates; Thiopental; Urinary Tract; Urology

Topics: Barbiturates; Convulsive Therapy; Electroconvulsive Therapy; Electroencephalography; Succinylcholine; Thiopental

Topics: Analgesia; Anesthesia; Anesthesia and Analgesia; Autonomic Agents; Barbiturates; Ether; Genitalia; Genitalia, Female; Gynecology; Phenothiazines; Stupor; Thiopental

Topics: Anesthetics, Intravenous; Barbiturates; Humans; Thiopental

Topics: Barbiturates; Brain; Depression; Depressive Disorder; Humans; Thiopental

Topics: Analgesia; Anesthesia; Anesthesia and Analgesia; Barbiturates; Ethers; Guaifenesin; Muscle Relaxants, Central; Thiopental

Topics: Administration, Rectal; Analgesia; Anesthesia; Anesthesia and Analgesia; Barbiturates; Thiopental

Topics: Analgesia; Anesthesia; Anesthesia and Analgesia; Anesthesia, Intravenous; Barbiturates; Genitalia; Genitalia, Female; Pain Management; Thiopental

Topics: Analgesia; Anesthesia; Anesthesia and Analgesia; Anesthesia, Intravenous; Barbiturates; Genitalia; Genitalia, Female; Narcotics; Pain Management; Thiopental

Topics: Analgesia; Anesthesia; Anesthesia and Analgesia; Anesthetics; Barbiturates; Thiopental

Topics: Analgesia; Anesthesia; Anesthesia and Analgesia; Anesthetics; Barbiturates; Thiopental

Topics: Anesthesia; Anesthesia, Intravenous; Anesthetics, Intravenous; Barbiturates; Gynecology; Thiopental

Topics: Anesthesia; Anesthesia, Intravenous; Anesthesiology; Female; Genitalia; Genitalia, Female; Gynecologic Surgical Procedures; Humans; Thiopental

Topics: Analgesia; Anesthesia; Anesthesia and Analgesia; Barbiturates; Narcotics; Thiopental