vasopressin--1-(1-mercaptocyclohexaneacetic-acid)-2-(o--methyl-l-tyrosine)-8-l-arginine- and Spinal-Cord-Injuries

Intracerebroventricular (i.c.v.) choline (50-150 microg) increased blood pressure and decreased heart rate in spinal cord transected, hypotensive rats. Choline administered intraperitoneally (60 mg/kg), also, increased blood pressure, but to a lesser extent. The pressor response to i.c.v. choline was associated with an increase in plasma vasopressin. Mecamylamine pretreatment (50 microg; i.c.v.) blocked the pressor, bradycardic and vasopressin responses to choline (150 microg). Atropine pretreatment (10 microg; i.c.v.) abolished the bradycardia but failed to alter pressor and vasopressin responses. Hemicholinium-3 [HC-3 (20 microg; i.c.v.)] pretreatment attenuated both bradycardia and pressor responses to choline. The vasopressin V1 receptor antagonist, (beta-mercapto-beta,beta-cyclopenta-methylenepropionyl1, O-Me-Tyr2, Arg8)-vasopressin (10 microg/kg) administered intravenously 5 min after choline abolished the pressor response and attenuated the bradycardia-induced by choline. These data show that choline restores hypotension effectively by activating central nicotinic receptors via presynaptic mechanisms, in spinal shock. Choline-induced bradycardia is mediated by central nicotinic and muscarinic receptors. Increase in plasma vasopressin is involved in cardiovascular effects of choline.

Topics: Animals; Antidiuretic Hormone Receptor Antagonists; Arginine Vasopressin; Atropine; Blood Pressure; Cerebral Ventricles; Choline; Dose-Response Relationship, Drug; Heart Rate; Hemicholinium 3; Hormone Antagonists; Hypotension; Injections, Intraventricular; Male; Rats; Rats, Wistar; Spinal Cord; Spinal Cord Injuries; Time Factors; Vasopressins