TACHYKININ RECEPTOR SUBTYPES INVOLVED IN THE CENTRAL EFFECTS OF TACHYKININS ON WATER AND SALT INTAKE

The present study was aimed at investigating which tachykinin receptor subtypes mediate the inhibitory effects of tachykinins a) on salt intake induced by sodium depletion, b) on water intake induced by subcutaneous hypertonic NaCl administration and c) on water intake induced by central angiotensin II injection. The study was carried out by evaluating the potency of action, following intracerebroventricular injection, of several peptides, including both naturally occurring tachykinins and synthetic peptides selective for a given receptor subtype. The results obtained show different rank orders of potency of the agonists in the different behavioral tests, thus suggesting that different receptor subtypes are involved in the effects of tachykinins on water and salt intake. NK-3 receptors appear to be involved in the inhibitory effect of tachykinins on depletion-induced salt appetite. NK-2 receptors apparently mediate the inhibitory effect of tachykinins on drinking induced by hyperosmotic NaCl administration, while NK-1 receptors are probably involved in the inhibition of angiotensin II-induced drinking.