Restoration of blood-pressure by choline treatment in rats made hypotensive by hemorrhage

Abstract

1 Intracerebroventricular (i.c.v.) injection of choline (25 - 150 mu g) 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 mu g or 50 mu g of choline, heart rate did not change, while 100 mu g or 150 pg i.c.v. choline produced a slight and short lasting bradycardia. Choline (150 mu g) failed to alter the circulating residual volume of blood in haemorrhaged rats. 2 The presser response to i.c.v. choline (50 mu g) in haemorrhaged rats was abolished by pretreatment with mecamylamine (50 mu g, i.c.v.) but not atropine (10 mu g, i.c.v.). The presser response to choline was blocked by pretreatment with hemicholinium-3 (20 mu g, i.c.v.). 3 The presser response to i.c.v. choline (150 mu g) was associated with a several fold increase in plasma levels of vasopressin and adrenaline but not of noradrenaline and plasma renin. 4 The presser response to i.c.v. choline (150 mu g) was not altered by bilateral adrenalectomy, but was attenuated by systemic administration of either phentolamine (10 mg kg(-1)) or the vasopressin antagonist [beta-mercapto-beta,beta-cyclopenta-methylenepropionyl(1), O-Me-Tyr(2),Arg(8)]-vasopressin (10 mu g kg(-1)). 5 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.