Effect of capsaicin and resiniferatoxin on gastrointestinal blood flow in rats.
The effect of capsaicin and resiniferatoxin on gastrointestinal blood flow was studied in anaesthetized rats by laser Doppler flowmetry. Resiniferatoxin injected into the jugular vein (0.08-1.6 nmol/kg) produced a marked and dose-dependent increase in gastric blood flow, while the effect of capsaicin (0.33-19.6 nmol/kg) was transient, variable and accompanied by profound systemic blood pressure changes. After acute bilateral cervical vagotomy combined with sympathetic neurone blockade (guanethidine 16 mumol/kg) or alpha-adrenoceptor blockade (phentolamine 1.6 mumol/kg), the vasodilator response to injected resiniferatoxin was more pronounced, indicating that the resiniferatoxin-induced gastric vasodilatation is not due to reflexes via parasympathetic or sympathetic efferent fibres. Resiniferatoxin given i.v. (0.08-0.64 nmol/kg) evoked a similar increase in the blood flow of the jejunum. Capsaicin (0.33-33 microM) or resiniferatoxin (0.16-1.6 microM) applied topically to the serosal surface of the stomach or jejunum produced a pronounced and long-lasting increase in blood flow after vagotomy and guanethidine treatment. The blood flow and blood pressure responses to capsaicin and resiniferatoxin were absent in rats desensitized with systemic capsaicin pretreatment. These laser Doppler data provide the first evidence for the effect of resiniferatoxin on gastrointestinal microcirculation and indicate the advantages of this agent and technique to study the sensory-efferent function of capsaicin-sensitive fibres.
Abdel Salam
O M
OM
First Department of Medicine, Medical University of Pécs, Hungary.
Szolcsányi
J
J
Pórszász
R
R
Mózsik
G
G
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D002211:Capsaicin / Q000008:administration & dosage / Q000494:pharmacology*; D004224:Diterpenes / Q000008:administration & dosage / Q000494:pharmacology*; D006145:Guanethidine / Q000494:pharmacology; D007275:Injections, Intravenous; D007545:Isoproterenol / Q000494:pharmacology; D007583:Jejunum / Q000098:blood supply; D017078:Laser-Doppler Flowmetry; D008297:Male; D009476:Neurons, Efferent / Q000187:drug effects; D010646:Phentolamine / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012039:Regional Blood Flow / Q000187:drug effects; D013270:Stomach / Q000098:blood supply*; D013563:Sympathectomy, Chemical; D014628:Vagotomy; D014665:Vasodilator Agents / Q000494:pharmacology
D004224:Diterpenes; D014665:Vasodilator Agents; C024353:resiniferatoxin; D007545:Isoproterenol; D002211:Capsaicin; D010646:Phentolamine; D006145:Guanethidine