CENTRAL CHOLINE REVERSES HYPOTENSION CAUSED BY ALPHA-ADRENOCEPTOR OR GANGLION BLOCKADE IN RATS - THE ROLE OF VASOPRESSIN

The effect of intracerebrovenricularly (i.c.v.) injected choline on bl ood pressure was investigated in rats made hypotensive by blocking per ipheral alpha-adrenoceptors or autonomic ganglionic transmission. Chol ine (50-150 mu g; i.c.v.) increased blood pressure in a dose-dependent manner and 150 mu g of choline restored blood pressure to the resting level. The presser response to choline was associated with an increas e in plasma vasopressin levels. Pretreatment with mecamylamine (50 mu g; i.c.v.), but not atropine (10 mu g; i.c.v.), blocked both the press er and vasopressin responses to i.c.v. choline. The vasopressin recept or antagonist, hylene-propionyl(1),O-Me-Try(2),Arg(8)]vasopressin (10 mu g/kg; i.v.), given 5 min after i.c.v. choline (150 mu g), abolished the presser effect of choline acid blood pressure returned to the pre -choline levels. It is concluded that the precursor of acetylcholine, choline, can increase blood pressure and reverse hypotension in alpha- adrenoceptor or ganglionic transmission blocked rats, by increasing pl asma vasopressin.