capsazepine and Hyperemia

The initial, rapid increase in skin blood flow in response to direct application of heat is thought to be mediated by an axon reflex, which is dependent on intact cutaneous sensory nerves. We tested the hypothesis that inhibition of transient receptor potential vanilloid type 1 (TRPV-1) channels, which are putative channels located on sensory nerves, would attenuate the skin blood flow response to local heating in humans. Ten subjects were equipped with four microdialysis fibres which were randomly assigned one of four treatments: (1) vehicle control (90% propylene glycol + 10% lactated Ringer solution); (2) 20 mm capsazepine to inhibit TRPV-1 channels; (3) 10 mm l-NAME to inhibit NO synthase; and (4) combined 20 mm capsazepine + 10 mm l-NAME. Following baseline measurements, the temperature of skin heaters was increased from 33°C to 42°C at a rate of 1.0°C every 10 s and local temperature was held at 42°C for 20-30 min until a stable plateau in skin blood flow was achieved. An index of skin blood flow was measured directly over each microdialysis site via laser-Doppler flowmetry (LDF). Beat-by-beat blood pressure was measured via photoplethysmography and verified via automated brachial auscultation. At the end of the local heating protocol, temperature of the heaters was increased to 43°C and 28 mm nitroprusside was infused to achieve maximal vasodilatation. Cutaneous vascular conductance (CVC) was calculated as LDF/mean arterial pressure and normalized to maximal values (%CVCmax). Initial peak in capsazepine (44 ± 4%CVCmax), l-NAME (56 ± 4%CVCmax) and capsazepine + l-NAME (32 ± 6%CVCmax) sites was significantly attenuated compared to control (87 ± 5%CVCmax; P < 0.001 for all conditions). The plateau phase of thermal hyperaemia was significantly attenuated in capsazepine (73 ± 6%CVCmax), l-NAME (47 ± 5%CVCmax) and capsazepine + l-NAME (31 ± 7%CVCmax) sites compared to control (92 ± 5%CVCmax; P < 0.001 for all conditions). These data suggest TRPV-1 channels contribute substantially to the initial peak and modestly to the plateau phases of thermal hyperaemia. These data further suggest a portion of the NO component of thermal hyperaemia may be due to activation of TRPV-1 channels.

Topics: Adult; Capsaicin; Enzyme Inhibitors; Female; Hot Temperature; Humans; Hyperemia; Male; NG-Nitroarginine Methyl Ester; Nitric Oxide; Nitric Oxide Synthase; Regional Blood Flow; Sensory Receptor Cells; Skin; Skin Temperature; TRPV Cation Channels

Topics: Anesthetics, Local; Capsaicin; Hot Temperature; Humans; Hyperemia; Lidocaine; Lidocaine, Prilocaine Drug Combination; Nitric Oxide; Prilocaine; Regional Blood Flow; Sensory Receptor Cells; Skin; TRPV Cation Channels

Acid in the oesophageal lumen is often sensed as heartburn. It was hypothesised that luminal CO(2), a permeant gas, rather than H(+), permeates through the epithelium, and is converted to H(+), producing an afferent neural signal by activating chemosensors.. The rat lower oesophageal mucosa was superfused with pH 7.0 buffer, and pH 1.0 or pH 6.4 high CO(2) (P(CO2) = 260 Torr) solutions with or without the cell-permeant carbonic anhydrase (CA) inhibitor methazolamide (MTZ, 1 mM), the cell-impermeant CA inhibitor benzolamide (BNZ, 0.1 mM), the transient receptor potential vanilloid 1 (TRPV1) antagonist capsazepine (CPZ, 0.5 mM) or the acid-sensing ion channel (ASIC) inhibitor amiloride (0.1 mM). Interstitial pH (pH(int)) was measured with 5',6'-carboxyfluorescein (5 mg/kg intravenously) loaded into the interstitial space, and blood flow was measured with laser-Doppler.. Perfusion of a high CO(2) solution induced hyperaemia without changing pH(int), mimicking the effect of pH 1.0 perfusion. Perfused MTZ, BNZ, CPZ and amiloride all inhibited CO(2)-induced hyperaemia. CA XIV was expressed in the prickle cells, with CA XII in the basal cells. TRPV1 was expressed in the stratum granulosum and in the muscularis mucosa, whereas all ASICs were expressed in the prickle cells, with ASIC3 additionally in the muscularis mucosa.. The response to CO(2) perfusion suggests that CO(2) diffuses through the stratum epithelium, interacting with TRPV1 and ASICs in the epithelium or in the submucosa. Inhibition of the hyperaemic response to luminal CO(2) by CA, TRPV1 and ASIC inhibitors implicates CA and these chemosensors in transduction of the luminal acid signal. Transepithelial CO(2) permeation may explain how luminal H(+) equivalents can rapidly be transduced into hyperaemia, and the sensation of heartburn.

Topics: Acid Sensing Ion Channels; Amiloride; Animals; Benzolamide; Capsaicin; Carbon Dioxide; Carbonic Anhydrase Inhibitors; Epithelial Cells; Esophageal pH Monitoring; Esophagus; Gastroesophageal Reflux; Hyperemia; Male; Methazolamide; Mucous Membrane; Nerve Tissue Proteins; Rats; Rats, Sprague-Dawley; Sodium Channels; TRPV Cation Channels

The duodenal mucosa is exposed to PCO(2) >200 mm Hg due to the luminal mixture of gastric acid with secreted bicarbonate, which augments mucosal protective mechanisms. We examined the hyperemic response to elevated luminal PCO(2) in the duodenum of anesthetized rats luminally exposed to high CO(2) saline to help elucidate luminal acid-sensing mechanisms.. Blood flow was measured by laser Doppler, and intracellular pH of epithelial cells by measured by ratio microimaging. The permeant carbonic anhydrase (CA) inhibitor methazolamide, relatively impermeant CA inhibitor benzolamide, vanilloid receptor antagonist capsazepine, or sodium-hydrogen exchanger 1 (NHE-1) inhibitor dimethyl amiloride were perfused with or without the high CO(2) solution.. The high CO(2) solution increased duodenal blood flow, which was abolished by pretreatment with methazolamide or capsazepine or by dimethyl amiloride coperfusion. Sensory denervation with capsaicin also abolished the CO(2) effects. Benzolamide dose-dependently inhibited CO(2)-induced hyperemia and at 100 nmol/L inhibited CO(2)-induced intracellular acidification. The membrane-bound CA isoforms IV, IX, XII, and XIV and cytosolic CA II and the vanilloid receptor 1 (TRPV1) were expressed in duodenum and stomach. Dorsal root ganglion and nodose ganglion expressed all isoforms except for CA IX.. The duodenal hyperemic response to luminal CO(2) is dependent on cytosolic and membrane-bound CA isoforms, NHE-1, and TRPV1. CO(2)-induced intracellular acidification was inhibited by selective extracellular CA inhibition, suggesting that CO(2) diffusion across the epithelial apical membrane is mediated by extracellular CA. NHE-1 activation preceding TRPV1 stimulation suggests that luminal CO(2) is sensed as H(+) in the subepithelium.

Topics: Amiloride; Animals; Benzolamide; Blood Flow Velocity; Capsaicin; Carbon Dioxide; Carbonic Anhydrase Inhibitors; Carbonic Anhydrases; Disease Models, Animal; Duodenum; Epithelial Cells; Gene Expression; Hydrogen-Ion Concentration; Hyperemia; Intestinal Mucosa; Intracellular Fluid; Laser-Doppler Flowmetry; Male; Methazolamide; Rats; Rats, Sprague-Dawley; Reverse Transcriptase Polymerase Chain Reaction; RNA; Sodium-Calcium Exchanger; TRPV Cation Channels

Hyperdynamic circulation and mesenteric hyperaemia are found in cirrhosis. To delineate the role of endocannabinoids in these changes, we examined the cardiovascular effects of anandamide, AM251 (CB(1) antagonist), AM630 (CB(2) antagonist) and capsazepine (VR1 antagonist), in a rat model of cirrhosis.. Cirrhosis was induced by bile duct ligation. Controls underwent sham operation. Four weeks later, diameters of mesenteric arteriole and venule (intravital microscopy), arterial pressure, cardiac output, systemic vascular resistance and superior mesenteric artery (SMA) flow were measured after anandamide, AM251 (with or without anandamide), AM630 and capsazepine administration. CB(1), CB(2) and VR1 receptor expression in SMA was assessed by western blot and RT-PCR.. Anandamide increased mesenteric vessel diameter and flow, and cardiac output in cirrhotic rats, but did not affect controls. Anandamide induced a triphasic arterial pressure response in controls, but this pattern differed markedly in cirrhotic rats. Pre-administration of AM251 blocked the effects of anandamide. AM251 (without anandamide) increased arterial pressure and systemic vascular resistance, constricted mesenteric arterioles, decreased SMA flow and changed cardiac output in a time-dependent fashion in cirrhotic rats. Capsazepine decreased cardiac output and mesenteric arteriolar diameter and flow, and increased systemic vascular resistance in cirrhotic rats, but lacked effect in controls. Expression of CB(1) and VR1 receptor proteins were increased in cirrhotic rats. AM630 did not affect any cardiovascular parameter in either group.. These data suggest that endocannabinoids contribute to hyperdynamic circulation and mesenteric hyperaemia in cirrhosis, via CB(1)- and VR1-mediated mechanisms.

Topics: Animals; Arachidonic Acids; Bile Ducts; Blood Flow Velocity; Blood Pressure; Blotting, Western; Capsaicin; Cardiac Output; Disease Models, Animal; Endocannabinoids; Hyperemia; Indoles; Liver Circulation; Liver Cirrhosis, Biliary; Male; Mesenteric Artery, Superior; Piperidines; Polyunsaturated Alkamides; Pyrazoles; Rats; Rats, Sprague-Dawley; Receptor, Cannabinoid, CB1; Receptor, Cannabinoid, CB2; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Splanchnic Circulation; Time Factors; TRPV Cation Channels; Vascular Resistance; Vasodilation; Vasodilator Agents

We tested the hypothesis that the duodenal hyperemic response to acid occurs through activation of capsaicin-sensitive afferent nerves with subsequent release of vasodilatory substances such as calcitonin gene-related peptide (CGRP) and nitric oxide (NO). Laser-Doppler flowmetry was used to measure duodenal blood flow in urethan-anesthetized rats. Duodenal mucosa was superfused with pH 7. 0 buffer with capsaicin or bradykinin or was acid challenged with pH 2.2 solution, with or without vanilloid receptor antagonists, a CGRP receptor antagonist, an NO synthase (NOS) inhibitor, or a cyclooxygenase inhibitor. The selective vanilloid receptor antagonist capsazepine (CPZ) dose dependently inhibited the hyperemic response to acid and capsaicin but did not affect bradykinin-induced hyperemia. Ruthenium red was less inhibitory than capsazepine. Selective ablation of capsaicin-sensitive nerves, CGRP-(8-37), and N(G)-nitro-L-arginine methyl ester inhibited acid-induced hyperemia, but indomethacin did not. We conclude that luminal acid, but not bradykinin, stimulates CPZ-sensitive receptors on capsaicin-sensitive afferent nerves of rat duodenum. Activation of these receptors produces vasodilation via the CGRP-NO pathway but not via the cyclooxygenase pathway. Acid appears to be the endogenous ligand for duodenal vanilloid receptors.

Topics: Acids; Animals; Bradykinin; Capsaicin; Chemoreceptor Cells; Duodenum; Hyperemia; Male; Rats; Rats, Sprague-Dawley; Receptors, Drug; Regional Blood Flow; Time Factors

The mesenteric hyperemia induced by intraduodenal application of hydrochloric acid (HCl) is mediated in part by capsaicin-sensitive afferent nerves. Antagonist of capsaicin-sensitive receptors (capsazepine) and blocker of capsaicin-sensitive cation channels (ruthenium red) have been described. We employed these tools to dissect the mechanism of regulation of mesenteric hyperemia induced by intraduodenal administration of HCl. Subcutaneous 100 micromol/kg capsazepine or intraduodenal 0.1% ruthenium red was administered to pentobarbital anesthetized rats. Then, 2.5 ml/kg of 640 microM capsaicin or 0.1 N HCl was administered intraduodenally. The mesenteric hyperemic responses were recorded. The results demonstrated that in a dose that decreased the mesenteric hyperemia induced by intraduodenal capsaicin, capsazepine failed to attenuate the mesenteric vasodilatory effect of intraduodenal HCl. Ruthenium red significantly attenuated the mesenteric hyperemia after intraduodenal capsaicin and HCl. These in vivo data provide the first functional evidence for the existence of capsazepine-sensitive capsaicin receptors and cation channel complexes in the rat duodenal and intestinal mucosa. The capsaicin- and HCl-sensitive receptors are unlikely to be functionally identical in these locations. The ruthenium red-sensitive cation channels appear to mediate the capsaicin- and HCl-induced mesenteric hyperemia.

Topics: Animals; Blood Pressure; Capsaicin; Duodenum; Hydrochloric Acid; Hyperemia; Laser-Doppler Flowmetry; Male; Mesenteric Arteries; Rats; Rats, Sprague-Dawley; Regional Blood Flow; Ruthenium Red