dynorphins and Body-Weight

Undernutrition limits reproduction through inhibition of gonadotropin-releasing hormone (GnRH)/luteinizing hormone (LH) secretion. Because KNDy neurons coexpress neuropeptides that play stimulatory (kisspeptin and neurokinin B [NKB]) and inhibitory (dynorphin) roles in pulsatile GnRH/LH release, we hypothesized that undernutrition would inhibit kisspeptin and NKB expression at the same time as increasing dynorphin expression. Fifteen ovariectomized lambs were either fed to maintain pre-study body weight (controls) or feed-restricted to lose 20% of pre-study body weight (FR) over 13 weeks. Blood samples were collected and plasma from weeks 0 and 13 were assessed for LH by radioimmunoassay. At week 13, animals were killed, and brain tissue was processed for assessment of KNDy peptide mRNA or protein expression. Mean LH and LH pulse amplitude were lower in FR lambs compared to controls. We observed lower mRNA abundance for kisspeptin within KNDy neurons of FR lambs compared to controls with no significant change in mRNA for NKB or dynorphin. We also observed that FR lambs had fewer numbers of arcuate nucleus kisspeptin and NKB perikarya compared to controls. These findings support the idea that KNDy neurons are important for regulating reproduction during undernutrition in female sheep.

Topics: Animals; Arcuate Nucleus of Hypothalamus; Body Weight; Dynorphins; Female; Gonadotropin-Releasing Hormone; Kisspeptins; Malnutrition; Neurokinin B; Neurons; RNA, Messenger; Sheep

Several studies have reported that nicotine, the main bioactive component of tobacco, exerts a marked negative energy balance. Apart from its anorectic action, nicotine also modulates energy expenditure, by regulating brown adipose tissue (BAT) thermogenesis and white adipose tissue (WAT) browning. These effects are mainly controlled at the central level by modulation of hypothalamic neuropeptide systems and energy sensors, such as AMP-activated protein kinase (AMPK). In this study, we aimed to investigate the kappa opioid receptor (κOR)/dynorphin signaling in the modulation of nicotine's effects on energy balance. We found that body weight loss after nicotine treatment is associated with a down-regulation of the κOR endogenous ligand dynorphin precursor and with a marked reduction in κOR signaling and the p70 S6 kinase/ribosomal protein S6 (S6K/rpS6) pathway in the lateral hypothalamic area (LHA). The inhibition of these pathways by nicotine was completely blunted in κOR deficient mice, after central pharmacological blockade of κOR, and in rodents where κOR was genetically knocked down specifically in the LHA. Moreover, κOR-mediated nicotine effects on body weight do not depend on orexin. These data unravel a new central regulatory pathway modulating nicotine's effects on energy balance.

Topics: AMP-Activated Protein Kinases; Animals; Body Weight; Dynorphins; Energy Metabolism; Hypothalamic Area, Lateral; Male; Mice; Mice, Inbred C57BL; Nicotine; Rats; Rats, Sprague-Dawley; Receptors, Opioid, kappa; Signal Transduction

The neuronal regulation of metabolic and behavioral responses to different diets and feeding regimens is an important research area. Herein, we investigated if the opioid peptide dynorphin modulates feeding behavior and metabolism. Mice lacking dynorphin peptides (KO) were exposed to either a normal diet (ND) or a high-fat diet (HFD) for a period of 12 weeks. Additionally, mice had either time-restricted (TR) or ad libitum (AL) access to food. Body weight, food intake and blood glucose levels were monitored throughout the 12-week feeding schedule. Brain samples were analyzed by immunohistochemistry to detect changes in the expression levels of hypothalamic peptides. As expected, animals on HFD or having AL access to food gained more weight than mice on ND or having TR access. Unexpectedly, KO females on TR HFD as well as KO males on AL ND or AL HFD demonstrated a significantly increased body weight gain compared to the respective WT groups. The calorie intake differed only marginally between the genotypes: a significant difference was present in the female ND AL group, where dynorphin KO mice ate more than WT mice. Although female KO mice on a TR feeding regimen consumed a similar amount of food as WT controls, they displayed significantly higher levels of blood glucose. We observed significantly reduced levels of hypothalamic orexigenic peptides neuropeptide Y (NPY) and orexin-A in KO mice. This decrease became particularly pronounced in the HFD groups and under AL condition. The kappa opiod receptor (KOR) levels were higher after HFD compared to ND feeding in the ventral pallidum of WT mice. We hypothesize that HFD enhances dynorphin signaling in this hedonic center to maintain energy homeostasis, therefore KO mice have a more pronounced phenotype in the HFD condition due to the lack of it. Our data suggest that dynorphin modulates metabolic changes associated with TR feeding regimen and HFD consumption. We conclude that the lack of dynorphin causes uncoupling between energy intake and body weight gain in mice; KO mice maintained on HFD become overweight despite their normal food intake. Thus, using kappa opioid receptor agonists against obesity could be considered as a potential treatment strategy.

Topics: Animals; Blood Glucose; Body Weight; Brain; Diet, High-Fat; Dynorphins; Feeding Behavior; Female; Gene Knockout Techniques; Male; Mice

The dynorphin (DYN) peptide family includes opioid and non-opioid peptides, yet the physiological role of the non-opioid DYN peptides remains poorly understood. Recent evidence shows that administering the non-opioid peptide DYN-A

Topics: Adiposity; Adrenocorticotropic Hormone; Animals; Body Weight; Central Nervous System Agents; Choice Behavior; Dynorphins; Energy Metabolism; Feeding Behavior; Male; Mice, Inbred BALB C; Orexins; Paraventricular Hypothalamic Nucleus; Peptide Fragments; Receptors, Corticotropin-Releasing Hormone; Running

In the human infundibular (arcuate) nucleus, a subpopulation of neurons coexpress kisspeptin and neurokinin B (NKB), 2 peptides required for normal reproductive function. A homologous group of neurons exists in the arcuate nucleus of rodents, termed KNDy neurons based on the coexpression of kisspeptin, NKB, and dynorphin. To study their function, we recently developed a method to selectively ablate KNDy neurons using NK3-SAP, a neurokinin 3 receptor agonist conjugated to saporin (SAP). Here, we ablated KNDy neurons in female rats to determine whether these neurons are required for estrous cyclicity and the steroid induced LH surge. NK3-SAP or Blank-SAP (control) was microinjected into the arcuate nucleus using stereotaxic surgery. After monitoring vaginal smears for 3-4 weeks, rats were ovariectomized and given 17β-estradiol and progesterone in a regimen that induced an afternoon LH surge. Rats were killed at the time of peak LH levels, and brains were harvested for NKB and dual labeled GnRH/Fos immunohistochemistry. In ovary-intact rats, ablation of KNDy neurons resulted in hypogonadotropic hypogonadism, characterized by low levels of serum LH, constant diestrus, ovarian atrophy with increased follicular atresia, and uterine atrophy. Surprisingly, the 17β-estradiol and progesterone-induced LH surge was 3 times higher in KNDy-ablated rats. Despite the marked increase in the magnitude of the LH surge, the number of GnRH or anterior ventral periventricular nucleus neurons expressing Fos was not significantly different between groups. Our studies show that KNDy neurons are essential for tonic levels of serum LH and estrous cyclicity and may play a role in limiting the magnitude of the LH surge.

Topics: Animals; Arcuate Nucleus of Hypothalamus; Body Weight; Dynorphins; Estradiol; Estrous Cycle; Female; Hypogonadism; Kisspeptins; Luteinizing Hormone; Neurokinin B; Neurons; Progesterone; Rats; Rats, Sprague-Dawley

Arcuate neurons that coexpress kisspeptin (Kiss1), neurokinin B (Tac2), and dynorphin (Pdyn) mediate negative feedback of 17β-estradiol (E2) on the HPG axis. Previous studies report that fasting and caloric restriction reduce arcuate Kiss1 expression. The objective of this study was to determine the interactions of E2 with fasting, caloric restriction, and diet-induced obesity on KNDy gene and receptor expression. Ovariectomized female mice were separated into control and estradiol benzoate (E2B)-treated groups. E2B decreased Kiss1 and the tachykinin 2 receptor, Tac3r, in ARC tissue and Tac2 in Tac2 neurons. Diet-induced obesity decreased Kiss1 in oil-treated animals and the kisspeptin receptor, Kiss1r and Tac3r in the ARC of E2B-treated animals. Chronic caloric (30%) restriction reduced all three neuropeptides in oil-treated females and Kiss1r by E2B in CR animals. Taken together, our experiments suggest that steroidal environment and energy state negatively regulate KNDy gene expression in both ARC and Tac2 neurons.

Topics: Animals; Arcuate Nucleus of Hypothalamus; Body Composition; Body Weight; Caloric Restriction; Diet; Diet, High-Fat; Dynorphins; Estradiol; Fasting; Female; Gene Expression Profiling; Gene Expression Regulation; Ghrelin; Kisspeptins; Mice, Inbred C57BL; Models, Biological; Neurokinin B; Neurons; Neuropeptides; Obesity; Organ Size; Signal Transduction

Electroacupuncture (EA) is used as a prescription to treat pruritus and atopic dermatitis. Whether EA affects experimental itch in rat models of immunologic or neuronal damages, however, is unknown.. The present study was designed to determine the therapeutic effects of high-frequency EA on atopic dermatitis-like lesions in rats.. Capsaicin (50mg/kg) was subcutaneously administered rat pups within 48h after birth. Rats then underwent 30min of EA at six acupoints (bilateral BL13, and unilateral LI11, ST36, SP10, SP6) every other day (EA group) for 3 weeks. Measurements of IgE, mast cells, scratching behavior, dynorphin release, skin thickness and dermatitis score were obtained.. Only the dermatitis score and dynorphin expression were decreased in the EA group compared with the control non-EA group.. We suggest that high-frequency EA alleviates pruritus of atopic dermatitis-like lesions in rats induced by capsaicin injection, via the release of dynorphin. These findings indicate a new potential therapeutic approach for the amelioration of symptoms of atopic dermatitis.

Topics: Animals; Animals, Newborn; Body Weight; Capsaicin; Dermatitis; Dermatitis, Atopic; Disease Models, Animal; Dynorphins; Electroacupuncture; Immunoglobulin E; Male; Mast Cells; Phenotype; Pruritus; Rats; Skin; Treatment Outcome

Orexigenic neuropeptide Y (NPY) and dynorphin (DYN) regulate energy homeostasis. Single NPY or dynorphin deletion reduces food intake or increases fat loss. Future developments of obesity therapeutics involve targeting multiple pathways. We hypothesised that NPY and dynorphin regulate energy homeostasis independently, thus double NPY and dynorphin ablation would result in greater weight and/or fat loss than the absence of NPY or dynorphin alone.. We generated single and double NPY and dynorphin knockout mice (NPYΔ, DYNΔ, NPYDYNΔ) and compared body weight, adiposity, feeding behaviour, glucose homeostasis and brown adipose tissue uncoupling protein-1 (UCP-1) expression to wildtype counterparts.. Body weight and adiposity were significantly increased in NPYDYNΔ, but not in NPYΔ or DYNΔ. This was not due to increased food intake or altered UCP-1 expression, which were not significantly altered in double knockouts. NPYDYNΔ mice demonstrated increased body weight loss after a 24-h fast, with no effect on serum glucose levels after glucose injection.. Contrary to the predicted phenotype delineated from single knockouts, double NPY and dynorphin deletion resulted in heavier mice, with increased adiposity, despite no significant changes in food intake or UCP-1 activity. This indicates that combining long-term opioid antagonism with blockade of NPY-ergic systems may not produce anti-obesity effects.

Topics: Adipose Tissue; Animals; Appetite Regulation; Body Weight; Dynorphins; Energy Metabolism; Female; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Neuropeptide Y; Obesity

Estrogen withdrawal increases gonadotropin secretion and body weight, but the critical cell populations mediating these effects are not well understood. Recent studies have focused on a subpopulation of hypothalamic arcuate neurons that coexpress estrogen receptor α, neurokinin 3 receptor (NK(3)R), kisspeptin, neurokinin B, and dynorphin for the regulation of reproduction. To investigate the function of kisspeptin/neurokinin B/dynorphin (KNDy) neurons, a novel method was developed to ablate these cells using a selective NK(3)R agonist conjugated to the ribosome-inactivating toxin, saporin (NK(3)-SAP). Stereotaxic injections of NK(3)-SAP in the arcuate nucleus ablated KNDy neurons, as demonstrated by the near-complete loss of NK(3)R, NKB, and kisspeptin-immunoreactive (ir) neurons and depletion of the majority of arcuate dynorphin-ir neurons. Selectivity was demonstrated by the preservation of proopiomelanocortin, neuropeptide Y, and GnRH-ir elements in the arcuate nucleus and median eminence. In control rats, ovariectomy (OVX) markedly increased serum LH, FSH, and body weight, and these parameters were subsequently decreased by treatment with 17β-estradiol. KNDy neuron ablation prevented the rise in serum LH after OVX and attenuated the rise in serum FSH. KNDy neuron ablation did not completely block the suppressive effects of E(2) on gonadotropin secretion, a finding consistent with redundant pathways for estrogen negative feedback. However, regardless of estrogen status, KNDy-ablated rats had lower levels of serum gonadotropins compared with controls. Surprisingly, KNDy neuron ablation prevented the dramatic effects of OVX and 17β-estradiol (E(2)) replacement on body weight and abdominal girth. These data provide evidence that arcuate KNDy neurons are essential for tonic gonadotropin secretion, the rise in LH after removal of E(2), and the E(2) modulation of body weight.

Topics: Animals; Arcuate Nucleus of Hypothalamus; Body Weight; Dynorphins; Estradiol; Estrogens; Female; Follicle Stimulating Hormone; Gonadotropin-Releasing Hormone; Gonadotropins; Immunohistochemistry; Immunotoxins; Kisspeptins; Luteinizing Hormone; Neurokinin B; Neurons; Neuropeptide Y; Ovariectomy; Pro-Opiomelanocortin; Rats; Rats, Sprague-Dawley; Ribosome Inactivating Proteins, Type 1; Saporins

Previously, we have reported that brain regions that are thought to be involved in motivated behavior are altered in animals undergoing repeated exposures to immobilization stress. The goal of the present study was to determine the effects of recovery from this type of stress on these same mesolimbic brain regions. For this purpose, adult male Sprague-Dawley rats were initially exposed to immobilization stress either once (2 h) or repeatedly (2 h×10 days). Rats were then either allowed to recover from the stressor for a shorter (2 days) or longer period of time (9 days) in their home cages. At the end of this recovery period, rats were euthanized and trunk blood and brains were processed for serum corticosterone (CORT) and neurochemistry, respectively. Brain mRNA levels were determined via in situ hybridization for the opioid preprodynorphin (DYN) and its cognate receptor (kappa, KOR), in striatal and accumbal subregions. A pattern of selective transcriptional activation emerged in the four resultant treatment conditions where a short recovery from either a single or repeated exposure to immobilization produced increases in KOR-mRNA levels in striatal and nucleus accumbens (Acb) subregions. Relative to controls, these differences were diminished after a longer recovery period. Interestingly, DYN-mRNA levels were unchanged after the shorter recovery period and after single or repeated immobilizations but appeared to be induced after a longer recovery period after repeated immobilizations. A relative amount of weight loss occurred after immobilization following repeated but not single exposure to stress. In addition, only those rats recovering from repeated stress exposures had higher CORT levels compared with non-immobilized controls. These results suggest that recovery from immobilization stress may alter the motivational system after as little as a single immobilization and that a possible dysphoric effect on appetitive behavior may be reflected by an altered striatal dynorphin system.

Topics: Analysis of Variance; Animals; Autoradiography; Body Weight; Corpus Striatum; Corticosterone; Dynorphins; Gene Expression Regulation; Immobilization; Male; Protein Precursors; Rats; Rats, Sprague-Dawley; Receptors, Opioid, kappa; Recovery of Function; RNA, Messenger; Stress, Psychological; Time Factors

Early environmental influences can change the neuronal development and thereby affect behavior in adult life. The aim in the present study was to thoroughly examine the impact of early environmental factors on endogenous opioids by using a rodent maternal separation (MS) model. The endogenous opioid peptide system is not fully developed at birth, and short- and/or long-term alterations may occur in these neural networks in animals exposed to manipulation of the postnatal environment. Rat pups were subjected to one of five rearing conditions; 15 min (MS15) litter (l) or individual (i), 360 min (MS360) l or i daily MS, or housed under normal animal facility rearing (AFR) conditions during postnatal days 1-21. Measurements of immunoreactive (ir) Met-enkephalin-Arg6Phe7 (MEAP) and dynorphin B (DYNB) peptide levels in the pituitary gland and in a number of brain areas, were performed at three and 10 weeks of age, respectively. MS-induced changes were more pronounced in ir MEAP levels, especially in individually separated rats at three weeks of age and in litter-separated rats at 10 weeks of age. The enkephalin and dynorphin systems have different developmental patterns, dynorphin appearing earlier, which may point at a more sensitive enkephalin system during the early postnatal weeks. The results provide evidence that opioid peptides are sensitive for early environmental factors and show that the separation conditions are critical and also result in changes manifesting at different time points. MS-induced effects were observed in areas related to stress, drug reward and dependence mechanisms. By describing effects on opioid peptides, the study addresses the possible role of a deranged endogenous opioid system in the previously described behavioral consequences of MS.

Topics: Age Factors; Animals; Animals, Newborn; Body Weight; Dynorphins; Endorphins; Enkephalin, Methionine; Environment; Female; Male; Maternal Behavior; Maternal Deprivation; Opioid Peptides; Pituitary Gland; Pregnancy; Rats; Rats, Wistar; Social Isolation; Stress, Psychological

This study was designed to investigate the effect of acute and chronic high-intensity treadmill exercise on changes in plasma lactate and brain neuropeptide (NPY), leucine-enkephalin (L-ENK), and dynorphin A(1-13) (DYN A(1-13)). Avidin-biotin complex (ABC) immunohistochemistry and image pattern analysis were used to observe the effect of chronic (total 7 weeks) and acute treadmill exercise (an initial speed of 15 m min(-1) gradually increased to 35 m min(-1) with 0 degrees, 20-25 min per day duration) on the changes of NPY, L-ENK, and DYN A(1-13) in different areas of rat brain. Plasma lactate was also measured in response to such exercise. Compared with preexercise control (P < 0.01), plasma lactate concentration significantly increased in the immediate postexercise; but it returned to the normal level soon after the 30 min postexercise. The content of NPY in paraventricular (PVN), dorsomedial (DMN), and ventromedial (VMN) hypothalamic nuclei continued to increase in 0, 30, and 180 min postexercise compared with preexercise control (P < 0.01). The content of L-ENK in caudate-putamen (CPu) significantly increased in the immediate postexercise compared with preexercise control (P < 0.01), but it gradually returned to the normal level after the 180 min postexercise. However, the content of DYN A(1-13) in PVN rose substantially only in 30 min postexercise in comparison with the preexercise control (P < 0.01). Thus, different changes of NPY, L-ENK, and DYN A(1-13) in response to such high-intensity exercise depend on the brain region and the time examined, especially, the contents of NPY in different brain regions continuously remain at a high level after such high-intensity exercise. And this high level might reduce energy expenditure and thus contribute to the stimulation of brain NPY neurons.

Topics: Animals; Body Weight; Brain Chemistry; Dynorphins; Enkephalin, Leucine; Lactic Acid; Male; Neuropeptide Y; Peptide Fragments; Physical Conditioning, Animal; Rats; Rats, Sprague-Dawley; Time Factors

The vulnerability to develop alcoholism is dependent on both genetic and environmental factors. The neurobiological mechanisms underlying these factors are not fully understood but individual divergence in the endogenous opioid peptide system may contribute. We have previously reported that early-life experiences can affect endogenous opioids and also adult voluntary ethanol intake. In the present study, this line of research was continued and the effects of long-term voluntary ethanol drinking on the opioid system are described in animals reared in different environmental settings. Rat pups were subjected to 15 min (MS15) or 360 min (MS360) of daily maternal separation during postnatal days 1-21. At 10 weeks of age, male rats were exposed to voluntary ethanol drinking in a four-bottle paradigm with 5%, 10% and 20% ethanol solution in addition to water for 2 months. Age-matched controls received water during the same period. Immunoreactive (ir) Met-enkephalin-Arg6Phe7 (MEAP) and dynorphin B (DYNB) peptide levels were thereafter measured in the pituitary gland and several brain areas. In water-drinking animals, lower ir MEAP levels were observed in the MS360 rats in the hypothalamus, medial prefrontal cortex, striatum and the periaqueductal gray, whereas no differences were seen in ir DYNB levels. Long-term ethanol drinking induced lower ir MEAP levels in MS15 rats in the medial prefrontal cortex and the periaqueductal gray, whereas higher levels were detected in MS360 rats in the hypothalamus, striatum and the substantia nigra. Chronic voluntary drinking affected ir DYNB levels in the pituitary gland, hypothalamus and the substantia nigra, with minor differences between MS15 and MS360. In conclusion, manipulation of the early environment caused changes in the opioid system and a subsequent altered response to ethanol. The altered sensitivity of the opioid peptides to ethanol may contribute to the previously reported differences in ethanol intake between MS15 and MS360 rats.

Topics: Alcohol Drinking; Animals; Animals, Newborn; Body Weight; Central Nervous System Depressants; Dose-Response Relationship, Drug; Dynorphins; Endorphins; Enkephalin, Methionine; Environment; Ethanol; Female; Male; Maternal Deprivation; Opioid Peptides; Pregnancy; Radioimmunoassay; Rats; Rats, Wistar; Risk; Stress, Psychological

Endogenous opioids, particularly dynorphins, have been implicated in regulation of energy balance, but it is not known how they mediate this in vivo. We investigated energy homeostasis in dynorphin knockout mice (Dyn(-/-) mice) and probed the interactions between dynorphins and the neuropeptide Y (NPY) system. Dyn(-/-) mice were no different from wild types with regards to body weight and basal and fasting-induced food intake, but fecal output was increased, suggesting decreased nutrient absorption, and they had significantly less white fat and lost more weight during a 24-h fast. The neuroendocrine and thermal responses to fasting were at least as pronounced in Dyn(-/-) as in wild types, and there was no stimulatory effect of dynorphin knockout on 24-h energy expenditure (kilocalories of heat produced) or physical activity. However, Dyn(-/-) mice showed increased circulating concentrations of 3,4-dihydroxyphenlacetic acid and 3,4-dihydroxyphenylglycol, suggesting increased activity of the sympathetic nervous system. The respiratory exchange ratio of male but not female Dyn(-/-) mice was reduced, demonstrating increased fat oxidation. Interestingly, expression of the orexigenic acting NPY in the hypothalamic arcuate nucleus was reduced in Dyn(-/-) mice. However, fasting-induced increases in pre-prodynorphin expression in the arcuate nucleus, the paraventricular nucleus, and the ventromedial hypothalamus but not the lateral hypothalamus were abolished by deletion of Y(1) but not Y(2) receptors. Therefore, ablation of dynorphins results in increases in fatty acid oxidation in male mice, reductions in adiposity, and increased weight loss during fasting, possibly via increases in sympathetic activity, decreases in intestinal nutrient absorption, and interactions with the NPYergic system.

Topics: Adipose Tissue; Animals; Body Weight; Dynorphins; Eating; Energy Metabolism; Fasting; Female; Glucose; Homeostasis; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Neuropeptide Y; Neurosecretory Systems; Physical Exertion; RNA, Messenger; Weight Loss

A common trait of antidepressant drugs, electroconvulsive treatment and physical exercise is that they relieve depression and up-regulate neurotrophic factors as well as cell proliferation and neurogenesis in the hippocampus. In order to identify possible biological underpinnings of depression and the antidepressant effect of running, we analysed cell proliferation, the level of the neurotrophic factor BDNF in hippocampus and dynorphin in striatum/accumbens in 'depressed' Flinders Sensitive Line rats (FSL) and Flinders Resistant Line (FRL) rats with and without access to running-wheels. The FRL strain exhibited a higher daily running activity than the FSL strain. Wheel-running had an antidepressant effect in the 'depressed' FSL rats, as indicated by the forced swim test. In the hippocampus, cell proliferation was lower in the 'depressed' rats compared to the control FRL rats but there was no difference in BDNF or dynorphin levels in striatum/accumbens. After 5 wk of running, cell proliferation increased in FSL but not in FRL rats. BDNF and dynorphin mRNA levels were increased in FRL but not to the same extent in the in FSL rats; thus, increased BDNF and dynorphin levels were correlated to the running activity but not to the antidepressant effect of running. The only parameter that was associated to basal level of 'depression' and to the antidepressant effect was cell proliferation in the hippocampus. Thus, suppression of cell proliferation in the hippocampus could constitute one of the mechanisms that underlie depression, and physical activity might be an efficient antidepressant.

Topics: Analysis of Variance; Animals; Antidepressive Agents; Behavior, Animal; Body Weight; Brain-Derived Neurotrophic Factor; Bromodeoxyuridine; Cell Count; Cell Proliferation; Depression; Disease Models, Animal; Dynorphins; Enkephalins; Freezing Reaction, Cataleptic; Hippocampus; Immunohistochemistry; In Situ Hybridization; Male; Rats; Rats, Inbred Strains; RNA, Messenger; Running; Substance P

This study examined the effects of chronic (14-day) steady-dose and escalating-dose "binge" pattern cocaine administration on striatal preprodynorphin (ppDyn) mRNA levels and behavioral stereotypies. Animals in the steady-state and escalating groups received cocaine in a "binge" pattern (three equal injections starting 30 min following the start of the daily light cycle, separated by 1 h). The dose of cocaine in the "steady-dose" group was 15 mg/kg/injection and remained constant throughout the study. The escalating group received 15 mg/kg/injection on days 1-3, 20 mg/kg/injection on days 4-6, 25 mg/kg/injection on days 7-9 and 30 mg/kg/injection thereafter, for a maximum daily dose of 90 mg/kg. Levels of ppDyn mRNA were determined by solution hybridization. Cocaine significantly affected body weight. Both steady-dose and escalating-dose "binge" cocaine administration resulted in expression of behavioral stereotypy and induced intense, rapid head movements which were dose- and time-dependent. Cocaine, independent of dose, increased ppDyn mRNA levels in the caudate putamen (CPu), but not in the nucleus accumbens (NAc). These data suggest that the ppDyn response to cocaine in the CPu is not dose-dependent or that it has reached a maximal level at the 45 mg/kg daily dose.

Topics: Analysis of Variance; Animals; Behavior, Animal; Body Weight; Cocaine; Corpus Striatum; Dopamine Uptake Inhibitors; Dose-Response Relationship, Drug; Drug Administration Schedule; Dynorphins; Gene Expression Regulation; Male; Protein Precursors; Rats; Rats, Inbred F344; RNA, Messenger; Stereotyped Behavior; Time Factors

The intracerebroventricular (i.c.v.) infusion of beta-endorphin can cause either a decrease in blood pressure in normal rats or an increase in obese rats. Diet-induced obesity is associated with an increase of hypothalamic mu opioid receptors. Since beta-endorphins act by opioid receptors, we investigated the effect of CNS mu as well as kappa opioid receptor agonist and antagonist on mean blood pressure (MAP), heart rate (HR) and renal sympathetic nerve activity (RSNA) in male Wistar rats fed either a high fat (HF) (40% fat by weight) or a regular low fat (control) (4% fat by weight) diet. After a 12-week-feeding period the animals were implanted with i.c.v. cannulas and 3-5 days later they were anesthetized and instrumented to record MAP, HR and RSNA. HF rats have higher MAP and the i.c.v. injection of a mu opioid agonist (DAMGO) initially decreased the MAP and then increased MAP, HR and RSNA in the normal animals. The increase was greater in HF animals. The i.c.v. injection of the mu antagonist (beta-FNA) resulted in a significantly greater decrease in MAP in HF animals. beta-FNA increased the RSNA in the HF rats but decreased it in the normal rats. The kappa agonist (dynorphin) decreased MAP in normal rats followed by a return to baseline, but not in HF rats. The kappa antagonist, nor-binaltorphimine (N-BP), increased MAP and RSNA in normal rats and to a lesser extent in HF rats. These findings suggest that rats given a high fat diet have higher blood pressures and a greater mu opioid-mediated responsiveness with a greater mu opioid-mediated autonomic tone. Additionally there is a decreased kappa responsiveness and tone in the HF rats. Both these changes, increased mu and decreased kappa responsiveness could strongly contribute to the increased blood pressure in obese animals.

Topics: Animals; Blood Pressure; Body Weight; Central Nervous System; Diet; Dose-Response Relationship, Drug; Dynorphins; Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; Male; Obesity; Rats; Rats, Wistar; Receptors, Opioid, kappa; Receptors, Opioid, mu; Time Factors

Various hypothalamic neuropeptides are involved in central regulation of food intake and expression of genes encoding these peptides changes with alterations in the bodyweight/metabolic status/nutritional status. Orexin(s) and dynorphin have been implicated in the regulation of appetite and neuroendocrine systems, but the function of these peptides is not well understood. We have employed in situ hybridization to examine the effects of long-term alterations in the bodyweight on expression of mRNA for preproorexin and prodynorphin in the putative feeding centers of the ovine hypothalamus. Expression of preproorexin was localized to the dorsomedial hypothalamic nucleus, perifornical area and lateral hypothalamic area. Cells expressing prodynorphin were localized to the periventricular, supraoptic, paraventricular, ventromedial hypothalamic nuclei and the thalamus. Small numbers of single scattered cells were seen in other brain areas. A few scattered prodynorphin-expressing cells were found in the lateral hypothalamic area but, in contrast to observations in the rat, there was no colocalization with preproorexin. Long-term alterations in the bodyweight did not influence the level of expression of preproorexin or prodynorphin. These findings suggest that orexin and dynorphin may not play a direct role in appetite regulation in sheep, although regulation at the level of the receptors for these peptides remains a possibility.

Topics: Animals; Appetite Regulation; Body Weight; Carrier Proteins; Dynorphins; Enkephalins; Feeding Behavior; Female; Food Deprivation; Gene Expression Regulation; Hypothalamus; Intracellular Signaling Peptides and Proteins; Neurons; Neuropeptides; Neurosecretory Systems; Orexins; Ovariectomy; Protein Precursors; RNA, Messenger; Sheep; Time Factors

Feeding behavior can be divided into appetitive and consummatory phases, differing in neural substrates and effects of deprivation. Opioids play an important role in the appetitive aspects of feeding, but they also have acute stimulatory effects on food consumption. Because the opioid peptide beta-endorphin is co-synthesized and released with melanocortins from proopiomelanocortin (POMC) neuronal terminals, we examined the physiological role of beta-endorphin in feeding and energy homeostasis using a strain of mutant mice with a selective deficiency of beta-endorphin. Male beta-endorphin-deficient mice unexpectedly became obese with ad libitum access to rodent chow. Total body weight increased by 15% with a 50-100% increase in the mass of white fat. The mice were hyperphagic with a normal metabolic rate. Despite the absence of endogenous beta-endorphin, the mutant mice did not differ from wild-type mice in their acute feeding responses to beta-endorphin or neuropeptide Y administered intracerebroventricularly or naloxone administered intraperitoneally. Additional mice were studied using an operant behavioral paradigm to examine their acquisition of food reinforcers under increasing work demands. Food-deprived, beta-endorphin-deficient male mice emitted the same number of lever presses under a progressive ratio schedule compared to wild-type mice. However, the mutant mice worked significantly less than did the wild-type mice for food reinforcers under nondeprived conditions. Controls for nonspecific effects on acquisition of conditioned learning, activity, satiety, and resistance to extinction revealed no genotype differences, supporting our interpretation that beta-endorphin selectively affects a motivational component of reward behavior under nondeprived conditions. Therefore, we propose that beta-endorphin may function in at least two primary modes to modulate feeding. In the appetitive phase, beta-endorphin release increases the incentive value of food as a primary reinforcer. In contrast, it appears that endogenous beta-endorphin may inhibit food consumption in parallel with melanocortins and that the orexigenic properties previously ascribed to it may actually be due to other classes of endogenous opioid peptides.

Topics: Adrenocorticotropic Hormone; Animals; beta-Endorphin; Body Weight; Brain; Conditioning, Operant; Dynorphins; Eating; Energy Metabolism; Enkephalins; Feeding Behavior; Female; Homeostasis; Male; Mice; Mice, Knockout; Pro-Opiomelanocortin

Environmental manipulations early in life may induce persistent alterations in adult behaviour and physiology. The underlying neural mechanisms of these responses are not yet clear. We have previously reported long-term changes in brain opioid peptide levels in male and female Sprague-Dawley rats after short periods (15 min, known as neonatal handling) of maternal separation (MS) until weaning. To study this further, we investigated behavioural and neurochemical effects of repeated MS in male Wistar rats. The rat pups were separated from their dams in litters for either 360 min (MS360) or 15 min (MS15) daily from postnatal day 1 to 21 or exposed to normal animal facility rearing. Behavioural analysis showed that MS360 rats had increased ultrasonic calls on postnatal day 5 compared to MS15 rats, but not on postnatal day 6. Moreover, the MS360 rats had more animals with higher frequency of calls at day 5 than 6 than the MS15 rats. Analysis of the opioid peptides dynorphin B and Met-enkephalin-Arg(6)Phe(7) with radioimmunoassay 7 weeks after the MS procedure, revealed long-term neurochemical changes in several brain areas and in the pituitary gland. Immunoreactive dynorphin B and Met-enkephalin-Arg(6)Phe(7) levels were affected in the hypothalamus and dynorphin B levels in the neurointermediate pituitary lobe, amygdala, substantia nigra and the periaqueductal gray. Together, these findings show that repeated periods of MS early in life in male Wistar rats affect the development of the ultrasonic call response and induce long-lasting and possibly permanent alterations in the opioid peptide systems.

Topics: Animals; Animals, Newborn; Behavior, Animal; Body Weight; Brain; Corticosterone; Dynorphins; Endorphins; Enkephalin, Methionine; Enkephalins; Female; Male; Maternal Deprivation; Opioid Peptides; Pituitary Gland; Protein Precursors; Radioimmunoassay; Rats; Rats, Wistar; Time Factors; Ultrasonics

Sprague-Dawley rats selectively bred for diet-induced obesity (DIO) or diet resistance (DR) were characterized on diets of differing energy content and palatability. Over 10 wk, DR rats on a high-energy (HE) diet (31% fat) gained weight similarly to DR rats fed chow (4.5% fat), but they became obese on a palatable liquid diet (Ensure). DIO rats gained 22% more weight on an HE diet and 50% more on Ensure than chow-fed DIO rats. DIO body weight gains plateaued when switched from HE diet to chow. But, Ensure-fed DIO rats switched to chow spontaneously reduced their intake and weight to that of rats switched from HE diet to chow. They also reduced their hypothalamic proopiomelanocortin and dynorphin but not neuropeptide Y mRNA expression by 17-40%. When reexposed to Ensure after 7 wk, they again overate and matched their body weights to rats maintained on Ensure throughout. All Ensure-fed rats had a selective reduction in dynorphin mRNA in the ventromedial hypothalamic nucleus. Thus genetic background, diet composition, and palatability interact to produce disparate levels of defended body weight and central neuropeptide expression.

Topics: Adipose Tissue; Animal Feed; Animals; Arcuate Nucleus of Hypothalamus; Body Weight; Diet; Dietary Sucrose; Dynorphins; Eating; Food, Formulated; Gene Expression; Leptin; Male; Neuropeptide Y; Obesity; Pro-Opiomelanocortin; Rats; Rats, Sprague-Dawley; RNA, Messenger

It has been suggested that an opioidergic feeding pathway exists between the nucleus of the solitary tract (NTS) and the central nucleus of the amygdala. We studied the following three groups of rats: 1) artificial cerebrospinal fluid (CSF) infused in the NTS, 2) naltrexone (100 microg/day) infused for 13 days in the NTS, and 3) artificial CSF infused in the NTS of rats pair fed to the naltrexone-infused group. Naltrexone administration resulted in a decrease in body weight and food intake. Also, naltrexone infusion increased dynorphin, but not enkephalin, gene expression in the amygdala, independent of the naltrexone-induced reduction in food intake. Gene expression of neuropeptide Y in the arcuate nucleus and neuropeptide Y peptide levels in the paraventricular nucleus did not change because of naltrexone infusion. However, naltrexone induced an increase in serum leptin compared with pair-fed controls. Thus chronic administration of naltrexone in the NTS increased dynorphin gene expression in the amygdala, further supporting an opioidergic feeding pathway between these two brain sites.

Topics: Amygdala; Animals; Body Weight; Dynorphins; Eating; Gene Expression; Leptin; Male; Naltrexone; Narcotic Antagonists; Rats; Rats, Sprague-Dawley; Receptors, Opioid; Solitary Nucleus

Our previous work has demonstrated that 100-Hz electroacupuncture (EA) or 100-Hz transcutaneous electrical nerve stimulation (TENS) was very effective in ameliorating the morphine withdrawal syndrome in rats and humans. The mechanism was obscure. (1) Rats were made dependent on morphine by repeated morphine injections (5-140 mg/kg, s.c., twice a day) for eight days. They were then given 100-Hz EA for 30 min 24 h after the last injection of morphine. A marked increase in tail flick latency (TFL) was observed. This effect of 100-Hz EA could be blocked by naloxone (NX) at 20 mg/kg, but not at 1 mg/kg, suggesting that 100-Hz EA-induced analgesia observed in morphine-dependent rats is mediated by kappa-opioid receptors. (2) A significant decrease of the concentration of dynorphin A (1-17) immunoreactivity (-ir) was observed in the spinal perfusate in morphine-dependent rats, that could be brought back to normal level by 100-Hz EA. (3) 100-Hz EA was very effective in suppressing NX-precipitated morphine withdrawal syndrome. This effect of EA could be prevented by intrathecal administration of nor-BNI (2.5 micrograms/20 microliters), a kappa-opioid receptor antagonist, or dynorphin A (1-13) antibodies (25 micrograms/20 microliters) administered 10 min prior to EA. In conclusion, while the steady-state spinal dynorphin release is low in morphine-dependent rats, it can be activated by 100-Hz EA stimulation, which may be responsible for eliciting an analgesic effect and ameliorating morphine withdrawal syndrome, most probably via interacting with kappa-opioid receptor at spinal level.

Topics: Animals; Body Weight; Dynorphins; Electroacupuncture; Male; Morphine; Naloxone; Narcotic Antagonists; Narcotics; Pain Measurement; Rats; Rats, Wistar; Receptors, Opioid, kappa; Substance Withdrawal Syndrome

It is established that dopamine (DA) controls the expression of preprodynorphin (PPDYN), preprotachykinin A (PPT-A) and preproenkephalin (PPE) mRNAs in striatal structures. Since cocaine, nicotine and ethanol enhance extracellular DA concentration, we have examined whether their repeated administration produced common changes in the expression of these mRNAs. Quantitative in situ hybridization histochemistry was performed in rats 2 h after a final challenge subsequent to repeated subcutaneous injections (3 X a day) of cocaine (12.5 mg/kg), nicotine (0.4 mg/kg) for 14 days and ethanol (160 mg/kg) for 7 days. In the dorsal striatum, cocaine produced simultaneous PPDYN and PPT-A mRNA increases without PPE mRNA change whereas nicotine and ethanol produced no modification. After cocaine, PPDYN mRNA was preferentially increased in striatal patch compartment. In the nucleus accumbens, the effects were more complex. In cocaine-treated rats, we measured concomitant increases of PPDYN and PPE mRNA in the rostral pole, an isolated induction of PPT-A mRNA signals in the core without any change in the two shell subregions: the cone and the ventral shell. In contrast, after nicotine and ethanol, the ventral shell was the only accumbal subregion which showed a neuropeptide mRNA alteration, nicotine leading to decreased PPDYN mRNA and ethanol to increased PPT-A mRNA contents. The neuropeptide regulation after chronic treatment with these psychostimulant drugs does not strictly conform to a general DA control scheme in the dorsal and the ventral striatum. The cocaine effects can be clearly distinguished from those of nicotine and ethanol in terms of neuropeptide regulation and striatal subregions affected.

Topics: Animals; Body Weight; Cocaine; Corpus Striatum; Drug Administration Schedule; Dynorphins; Enkephalins; Ethanol; In Situ Hybridization; Injections, Subcutaneous; Male; Nicotine; Nucleus Accumbens; Protein Precursors; Rats; Rats, Sprague-Dawley; RNA, Messenger; Tachykinins

To ascertain cocaine's effects in the fetus, we developed a nonhuman primate model in which pregnant monkeys were administered cocaine (3 mg/kg i.m.) or saline four times a day from day 20 through days 40-70 of a 165-day gestation. At the time of cesarean section, plasma levels of cocaine in fetal blood were 231 +/- 70 ng/ml. Fetal brains were examined using immunocytochemistry, in situ hybridization, receptor autoradiography, and nuclease protection assay analysis. No differences were found in the expression of tyrosine hydroxylase and dopamine receptor mRNAs by days 40-45 of gestation. However, by day 60 the midbrain of monkeys exposed to cocaine had significantly reduced expression of tyrosine hydroxylase, the rate-limiting enzyme in dopamine synthesis. Moreover, dopamine D1 and D2 receptor mRNAs were significantly elevated in the rostral forebrain as were D1 and D2 receptor binding sites in days 60-70 cocaine-exposed fetuses. Cocaine treatment from day 20 to days 60 and 70 of gestation also significantly increased the mRNA concentrations of dynorphin and enkephalin in the rostral forebrain. These findings suggest that in utero cocaine exposure has profound effects on the developing dopamine neurocircuitry.

Topics: Amniotic Fluid; Animals; Body Weight; Brain; Cocaine; Dopamine; Dynorphins; Embryonic and Fetal Development; Enkephalins; Female; Gene Expression Regulation, Developmental; Macaca mulatta; Mesencephalon; Metabolic Clearance Rate; Neurons; Pregnancy; Prosencephalon; Receptors, Dopamine D1; Receptors, Dopamine D2; RNA, Messenger; Transcription, Genetic

Psychomotor stimulants such as cocaine alter gene expression in neurons of the striatum. Whereas many of these effects are mediated by D1 dopamine receptors, the involvement of other dopamine receptor subtypes or neurotransmitters is likely. To distinguish between these possibilities, regulation by cocaine of immediate-early genes and genes encoding neuropeptides was analysed in mice that lack functional D1 receptors. Gene expression was examined with in situ hybridization histochemistry. In these animals, cocaine failed to induce the immediate-early genes c-fos and zif 268. In contrast, substance P expression was abnormally increased by this drug. These results demonstrate that some of the effects of cocaine on gene regulation are mediated via D1 receptor-dependent mechanisms, as evidenced by the absence of immediate-early gene induction in D1-deficient mice, whereas others also involve additional, non-D1 receptor mechanisms, as shown for substance P expression.

Topics: Animals; Base Sequence; Body Weight; Brain; Cocaine; Corpus Striatum; DNA-Binding Proteins; Dynorphins; Early Growth Response Protein 1; Enkephalins; Gene Expression Regulation; Genes, Immediate-Early; Heterozygote; Homozygote; Immediate-Early Proteins; In Situ Hybridization; Mice; Mice, Knockout; Molecular Sequence Data; Oligonucleotide Probes; Organ Size; Proto-Oncogene Proteins c-fos; Receptors, Dopamine D1; RNA, Messenger; Substance P; Transcription Factors; Transcription, Genetic; Transcriptional Activation

Lewis rats are more likely to self-administer various drugs of abuse than Fischer rats. Here these two strains of rats were compared with regard to basal brain opioid peptide levels and the response to chronic morphine treatment and to naloxone-precipitated withdrawal. Lewis rats had lower basal dynorphin peptides in the substantia nigra, striatum (not Leu-enkephalinArg6) and VTA (not dynorphin B) and the pituitary gland. Leu-enkephalinArg6 levels were also lower in these structures (with the exception of striatum which had higher levels) and in the nucleus accumbens. There were also strain differences in the response to chronic morphine treatment; in the nucleus accumbens, morphine treatment increased dynorphin A levels in Fischer rats only, in the ventral tegmental area effects were opposite with increased dynorphin levels in Fischer and decreased levels in Lewis rats, in the hippocampus dynorphin levels were markedly reduced in Lewis rats only. In Fischer rats, chronic morphine strongly affected peptide levels in the substantia nigra and striatum, whereas Lewis rats responded less in these areas. Leu-enkephalin, which derives from both prodynorphin and proenkephalin, and Met-enkephalin, which derives from proenkephalin, were affected by chronic morphine mainly in Fischer rats, increasing levels in most of the brain areas examined. The results in this study show (1) strain differences in basal levels of prodynorphin-derived opioid peptides, (2) the prodynorphin system to be differently influenced by morphine in Lewis rats than in Fischer rats and 3) the proenkephalin system to be influenced by chronic morphine in brain areas related to reward processes only in Fischer rats.

Topics: Amino Acid Sequence; Animals; Body Weight; Brain Chemistry; Drug Tolerance; Dynorphins; Enkephalins; Female; Male; Molecular Sequence Data; Morphine; Naloxone; Narcotic Antagonists; Rats; Rats, Inbred F344; Rats, Inbred Lew; Species Specificity; Substance Withdrawal Syndrome

Anorexia nervosa is associated with vasopressin, oxytocin and serotonin abnormalities. Because of the relationship between exercise and anorexia nervosa, we explored the weight-loss syndrome produced by wheel running in food-deprived rats. Its effects on regional vasopressin and oxytocin concentrations were determined under basal conditions and following systemic fluoxetine. Weight-matched, exercised and unexercised rats served as controls. Fluoxetine caused abnormalities in suprachiasmatic vasopressin and dynorphin A content and in thymus oxytocin content that did not occur in weight-matched or exercised controls. No syndrome-specific anomalies occurred in the hypothalamo-neurohypophysial system or dorsal vagal complex (DVC). However, weight reduction and fluoxetine increased circulating vasopressin; moderate exercise caused fluoxetine-induced elevations in posterior pituitary vasopressin and oxytocin; and, unlike the other groups, fluoxetine increased DVC oxytocin in freely fed unexercised rats. It was concluded that syndrome-specific vasopressin and oxytocin abnormalities occur that are not secondary to weight loss or moderate exercise; that weight loss or fluoxetine increases circulating vasopressin; that moderate exercise alters neurohypophysial vasopressin and oxytocin content; and that weight loss or exercise inhibits a fluoxetine-stimulated increase in DVC oxytocin. Finally, it was argued that the fluoxetine abnormalities indicate possible serotonin dysfunction in the syndrome.

Topics: Animals; Anorexia Nervosa; Behavior, Animal; Body Weight; Dynorphins; Eating; Fluoxetine; Male; Oxytocin; Physical Conditioning, Animal; Rats; Rats, Sprague-Dawley; Suprachiasmatic Nucleus; Supraoptic Nucleus; Vagus Nerve; Vasopressins

Twenty-one patients with anorexia nervosa and 35 normal-weight patients with bulimia underwent a series of CSF studies involving measurement of CSF dynorphin A 1-8 immunoreactivity during hospitalization in an eating-disorder treatment and research program. The control group consisted of 17 healthy volunteers. There were no statistically significant differences in CSF dynorphin A 1-8 measurements among groups or within a group at various stages of treatment. These results regarding dynorphin A 1-8 immunoreactivity are discussed in light of other evidence for altered opiate function in some eating-disorder patients.

Topics: Adult; Anorexia Nervosa; Body Weight; Brain; Bulimia; Dynorphins; Endorphins; Female; Humans; Peptide Fragments; Psychiatric Status Rating Scales; Receptors, Opioid

We have used a novel method to identify genes expressed in the hypothalamus which may be potentially involved in controlling food intake and energy metabolism. We assumed that food deprivation, a powerful stimulus of food intake, would stimulate the activity of neural pathways involved in feeding behavior which should be reflected in an increase in the synthesis of any relevant neuropeptide and its messenger RNA. A study of 5 neuropeptides in 5 strains of mice has identified neuropeptide Y (NPY) as a gene whose expression in the hypothalamus is controlled by nutritional status, suggesting that hypothalamic NPY neurons are a link in the neural network regulating feeding behavior and energy metabolism. In addition, we have studied the effect of the diabetes mutation on neuropeptide gene expression during fasting and refeeding. Our findings suggest that abnormal NPY and enkephalin gene expression in the hypothalamus may be two important determinants of the expression of the diabetes mutation.

Topics: Animals; Blotting, Northern; Body Weight; Diabetes Mellitus, Experimental; Dynorphins; Eating; Enkephalins; Fasting; Food Deprivation; Hypothalamus; Mice; Mice, Inbred Strains; Mice, Mutant Strains; Neuropeptide Y; RNA, Messenger; Somatostatin; Species Specificity; Thyrotropin-Releasing Hormone

We have recently demonstrated that the pineal neurohormone melatonin can enhance immune reactivity in normal mice and counteract the effects of acute stress or corticosterone treatment on antibody production, thymus weight and anti-viral resistance. These remarkable immunopharmacologic effects of melatonin were abolished by naltrexone, suggesting an involvement of the endogenous opioid system. Here we compared the immunopharmacologic action of beta-endorphin, dynorphin 1-13, leu-enkephalin and metenkephalin with that of melatonin in restraint-stressed or prednisolone-treated mice and in normal nonstressed animals. We found that beta-endorphin and dynorphin 1-13 can mimic the immunoenhancing and antistress effect of melatonin. However, at variance with the pineal neurohormone, these opioids were effective in umprimed mcie, too. We found also that restraint stress or prednisolone treatment decreases the immunopharmacologic potency of beta-endorphin and augments that of dynorphin 1-13. In fact, at the doses used, beta-endorphin enhanced the antibody response in normal but not in stressed or prednisolone-treated mice, while dynorphin 1-13 was effective only in counteracting the effect of stress or prednisolone treatment. Most interestingly, all these effects proved to be dependent on the time of administration, i.e. showed a circadian rhythm in analogy with the effects of melatonin. Again, naltrexone abolished all the opioid effects, indicating that their action was exerted via opioid receptors. These findings have important scientific and practical implications.

Topics: Adjuvants, Immunologic; Animals; beta-Endorphin; Body Weight; Circadian Rhythm; Dynorphins; Erythrocytes; Female; Hemolytic Plaque Technique; Melatonin; Mice; Mice, Inbred BALB C; Naltrexone; Organ Size; Prednisolone; Restraint, Physical; Stress, Psychological; Thymus Gland

We have previously reported that female obese Zucker rats are hypersensitive to painful stimuli and are resistant to the analgesic effects of morphine. In continuation we hypothesized that these phenomena are possibly the result of diminished population of opioid receptors, or an overabundance of dynorphin interfering with morphine analgesia. We now report that female obese Zucker rats have decreased concentrations of mu opioid receptors in whole brain and elevated levels of Dynorphin A(1-8) (DYN) in a brain area known to be associated with responses to nociceptive stimuli.

Topics: Animals; Body Weight; Brain; Dynorphins; Female; Hypothalamic Area, Lateral; Hypothalamus, Middle; Naloxone; Peptide Fragments; Periaqueductal Gray; Radioligand Assay; Rats; Rats, Zucker; Receptors, Opioid; Receptors, Opioid, kappa; Receptors, Opioid, mu

The stimulus specificity for enhancement of dynorphin gene expression in rat spinal cord was studied by combined measurements of the peptide dynorphin A 1-8 and preprodynorphin mRNA levels during peripheral inflammation induced by several agents. The density of kappa receptors, the putative receptor for dynorphin peptides, was examined using receptor binding with autoradiographic visualization. Mu and delta receptor classes were also studied. All inflammatory agents tested (carrageenan, phorbol ester, yeast and Freund's adjuvant) rapidly induced edema and thermal hyperalgesia. All agents also induced a rapid (within 8 h) elevation in dynorphin mRNA and, in comparison, a delayed (within 2 days) elevation of dynorphin A 1-8 peptide; peak peptide levels were reached at 4 days. No alteration of kappa, mu or delta receptor binding was observed at 4 h or 4 days post inflammation. The rapid development of thermal hyperalgesia and elevation of dynorphin mRNA and peptide content indicates that the involvement of dynorphin-containing neurons in nociceptive processing does not require a chronic abnormality and a dynamic picture of opioid modulation of sensory processing emerges. These data also demonstrate that activation of dynorphin biosynthesis in spinal cord is a feature common to hyperalgesia and peripheral inflammation and is not restricted to any one type of inflammatory agent. The lack of alteration in receptors suggests that the physiological effects of an increased biosynthesis are not accompanied by a concurrent down-regulation of opiate receptors.

Topics: Animals; Behavior, Animal; Body Weight; Dynorphins; Endorphins; Gene Expression Regulation; Hot Temperature; Hyperalgesia; Inflammation; Male; Peptide Fragments; Protein Precursors; Rats; Rats, Inbred Strains; Receptors, Opioid; Spinal Cord

beta-Chlornaltrexamine (beta-CNA) is a non-equilibrium opioid receptor antagonist which alkylates and inactivates opioid receptors. Because opioid peptides are thought to contribute to the regulation of food intake, we examined the effects of intracerebroventricular (icv) injections of beta-CNA on the food intake and body weight of male rats. We also tested the ability of beta-CNA to block food intake stimulated by selective agonists of kappa, mu and delta opioid receptors: dynorphin A2 (DYN), Tyr-D-Ala-Gly-(Me)Phe-Gly-ol (DAGO), and [(D-Ser2,Leu5]-enkephalin-Thr6 (DSLET). Treatment with beta-CNA caused a long-term (2-4 days) reduction in daily food intake and a concomitant reduction in body weight. An additional experiment indicated that the weight loss after beta-CNA treatment could be completely accounted for by the reduction in intake. beta-CNA treatment also abolished or greatly attenuated the feeding effects of DAGO, DSLET and DYN, even when these peptides were tested 26 hours after beta-CNA administration. The long duration of the effects of beta-CNA suggests that this compound will be a useful pharmacological tool in further study of the opioid feeding system.

Topics: Animals; Body Weight; Dynorphins; Eating; Endorphins; Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; Enkephalin, Leucine; Enkephalins; Male; Naltrexone; Oligopeptides; Rats; Rats, Inbred Strains; Receptors, Opioid

The effect of chronic neuroleptic treatment, using haloperidol or clozapine, on immunoreactive dynorphin peptide and substance P levels in basal ganglia of rats was examined. The drugs were administered i.p. in daily doses for 10 days (haloperidol 1 mg/kg and clozapine 10 mg/kg). Dynorphin A, dynorphin B and substance P were measured in substantia nigra, striatum, globus pallidus and hypothalamus using specific radioimmunoassays. The most prominent effects were observed with with clozapine which increased levels of all measured peptides in substantia nigra. Haloperidol only affected nigral substance P levels which declined, while nigral dynorphin peptide levels remained unchanged. In striatum, haloperidol slightly reduced dynorphin peptides while substance P was unaffected. Clozapine increased striatal substance P but the dynorphin peptides were not affected. Minor changes in dynorphin peptides found in globus pallidus and hypothalamus were not statistically reliable. Substance P was not changed in these structures after either of the two drugs. High molecular weight fragments (greater than or equal to 5,000) from the dynorphin precursor, proenkephalin B, were measured in substantia nigra and striatum using trypsin digestion and subsequent analysis of generated Leu-enkephalin-Arg6. These high molecular weight fragments were found to be affected in the same manner as the dynorphin peptides. This study indicates that the two types of neuroleptic drugs have different modes of interaction on peptide systems in basal ganglia of rats. Dynorphin peptides and substance P were also differentially affected.

Topics: Animals; Basal Ganglia; Body Weight; Clozapine; Dibenzazepines; Dynorphins; Haloperidol; Injections, Intraperitoneal; Male; Protein Precursors; Radioimmunoassay; Rats; Rats, Inbred Strains; Substance P

The possible role of dynorphin, an endogenous opioid peptide, in the regulation of appetite was studied in male genetically-obese (Zucker) rats and their litter mates of normal weight. Eighteen pairs were divided into 3 treatment groups: control, acutely dynorphin-treated (5 mg/rat), and implanted with Alzet mini-osmotic pumps containing 2 mg dynorphin to be delivered at a rate of 10 micrograms/hr. Body weights and food and water consumption were determined daily for 7 days. Body weights were not significantly changed from initial values for any treatment group. Food and water consumption per 24 hours were generally the same for obese rats and their normal littermates, but in terms of consumption per 100 g body weight, the obese rats generally consumed less food and water. Neither acute nor continuous dynorphin administration affected consummatory levels.

Topics: Animals; Body Weight; Drinking; Dynorphins; Eating; Food; Male; Rats; Rats, Zucker

Bilateral, radiofrequency lesions of the mediobasal arcuate hypothalamus (MBH) strongly depleted levels of immunoreactive (ir)-beta-endorphin (beta-EP) in the hypothalamus and other brain tissues: these changes reflect destruction of those beta-EP-containing perikarya which are located in the MBH. No change in plasma ir-beta-EP was seen. The ir-dynorphin (DYN) content of the hypothalamus was also depressed while that of ir-Met-enkephalin was unaffected. The fall in hypothalamic ir-beta-EP was correlated with the fall in that of ir-DYN. Lesioned rats displayed only a minor, transient reduction in rate of weight gain between days 3 and 9 postsurgery: this disappeared thereafter. Further, the lesion did not affect the pattern of weight loss and regain associated with 24 h food and water deprivation. Indeed, the total 24 h (daily) food intake (FI) and water intake (WI) of lesioned rats did not differ from that of sham animals while deprivation-induced hyperphagia and hyperdipsia was not attenuated by the lesions. Moreover, the ability of naltrexone to decrease FI and WI (during both dark and light phases of the daily cycle) was not altered by the lesions. These observations indicate that central beta-EP may not be essential for the maintenance of a normal 24 h FI and WI and that opioid antagonists do not act upon the MBH or upon central beta-EP neurones in their suppression of FI and WI. Further, they suggest that central beta-EP may not fulfil an essential role in the control of body weight in the rat. Lesioned rats did, however, reveal a shift in the diurnal rhythmicity of FI and WI reflected in a reduction in the dark:light ratios of these. An alteration in the diurnal rhythmicity of sleeping and core temperature, but not locomotor activity, was also seen. The shifts in hypothalamic ir-beta-EP and ir-DYN (but no other tissue levels of any peptide) were correlated with the magnitude of the shifts in diurnal rhythmicity of ingestive behaviour. Moreover, lesions caudal to the MBH (not affecting hypothalamic ir-beta-EP or ir-DYN) or dexamethasone treatment (which affects pituitary pools of ir-beta-EP and ir-DYN) did not modify these rhythms. Thus, in these respects, the effects are 'particular' to MBH lesions modifying hypothalamic ir-beta-EP and ir-DYN. The data suggest that the MBH may play a role in the modulation of the diurnal scheduling of ingestive behaviour in the rat.(ABSTRACT TRUNCATED AT 400 WORDS)

Topics: Animals; Arcuate Nucleus of Hypothalamus; Body Weight; Brain Chemistry; Circadian Rhythm; Dexamethasone; Dynorphins; Endorphins; Enkephalin, Methionine; Feeding Behavior; Food Deprivation; Male; Naltrexone; Rats; Rats, Inbred Strains

The hyperphagia and obesity induced by ventromedial hypothalamic (VMH) electrolytic lesions in female rats were associated with a 70-94% decrease in the level of beta-endorphin (beta-E) in the hypothalamus and other regions of brain, but not in the pituitary. Dynorphin (Dyn) and methionine-enkephalin (ME) levels were also decreased. Rats with VMH lesions were less sensitive to the inhibitory effect of naloxone on their food-intake. Mice injected with gold thioglucose (GTG) also showed a decrease in the hypothalamic content of beta-E and Dyn and exhibited 30% less analgesia compared to control mice after cold swim stress.

Topics: Analgesia; Animals; beta-Endorphin; Body Weight; Brain; Dynorphins; Enkephalin, Methionine; Feeding Behavior; Female; Pituitary Gland; Rats; Rats, Inbred Strains; Ventromedial Hypothalamic Nucleus