Evaluation for roles of periventricular cholinoceptors in vasopressin secretion in response to angiotensin II and an osmotic stimulus.

In conscious rats, intracerebroventricular (i.c.v.) injections (10 microliters) of carbachol (1.4 nmol), angiotensin II (AII; 48.2 pmol) or a hypertonic solution (990 mOsm/kg) produced increases of plasma vasopressin (AVP) and arterial pressure. The effects of carbachol were inhibited not by a nicotinic cholinergic blocker hexamethonium (28 nmol), but by a muscarinic cholinergic blocker atropine (28 nmol). However, neither hexamethonium nor atropine affected the AVP and pressor responses to AII or the hypertonic solution. We concluded that periventricular cholinoceptors may not be involved in the central actions of AII and hypertonicity on AVP release and blood pressure.