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 blood pressure was investigated in rats made hypotensive by blocking peripheral alpha-adrenoceptors or autonomic ganglionic transmission. Choline (50-150 micrograms; i.c.v.) increased blood pressure in a dose-dependent manner and 150 micrograms of choline restored blood pressure to the resting level. The pressor response to choline was associated with an increase in plasma vasopressin levels. Pretreatment with mecamylamine (50 micrograms; i.c.v.), but not atropine (10 micrograms; i.c.v.), blocked both the pressor and vasopressin responses to i.c.v. choline. The vasopressin receptor antagonist, [beta-mercapto-beta,beta-cyclopenta-methylene-propionyl1,O-Me-T ry2,Arg8] vasopressin (10 micrograms/kg; i.v.), given 5 min after i.c.v. choline (150 micrograms), abolished the pressor effect of choline and 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 plasma vasopressin.