Restoration of blood pressure by choline treatment in rats made hypotensive by haemorrhage

Abstract

Intracerebroventricular (i.c.v.) injection of choline (25–150 μg) increased blood pressure in rats made acutely hypotensive by haemorrhage. Intraperitoneal administration of choline (60 mg kg−1) also increased blood pressure, but to a lesser extent. Following i.c.v. injection of 25 μg or 50 μg of choline, heart rate did not change, while 100 μg or 150 μg i.c.v. choline produced a slight and short lasting bradycardia. Choline (150 μg) failed to alter the circulating residual volume of blood in haemorrhaged rats The pressor response to i.c.v. choline (50 μg) in haemorrhaged rats was abolished by pretreatment with mecamylamine (50 μg, i.c.v.) but not atropine (10 μg, i.c.v.). The pressor response to choline was blocked by pretreatment with hemicholinium‐3 (20 μg, i.c.v.) The pressor response to i.c.v. choline (150 μg) was associated with a several fold increase in plasma levels of vasopressin and adrenaline but not of noradrenaline and plasma renin The pressor response to i.c.v. choline (150 μg) was not altered by bilateral adrenalectomy, but was attenuated by systemic administration of either phentolamine (10 mg kg−1) or the vasopressin antagonist [β‐mercapto‐β,β‐cyclopenta‐methylenepropionyl1, O‐Me‐Tyr2,Arg8‐vasopressin (10 μg kg−1) It is concluded that the precursor of acetylcholine, choline, can increase and restore blood pressure in acutely haemorrhaged rats by increasing central cholinergic neurotransmission. Nicotinic receptor activation and an increase in plasma vasopressin and adrenaline level appear to be involved in this effect of choline. 1995 British Pharmacological Society