Central tachykinin injection potently suppresses the need-free salt intake of the female rat.

Repeated sodium depletions produce a persistent, enhanced need-free salt intake in the rat, particularly in the female. The neurochemical mechanisms underlying the phenomenon are still unknown. The present studies evaluated the effect on the enhanced need-free salt intake of the female rat (1) of pharmacological interference with the natriorexigenic hormones angiotensin II and aldosterone and (2) of the central injection of the tachykinin peptides, which are endowed with antinatriorexic activity. The need-free salt intake of the female rat is not modified by treatment with the angiotensin-converting enzyme inhibitor captopril or by the aldosterone receptor antagonist RU-28318. On the other hand, the behavior is highly sensitive to the inhibitory effect of central tachykinins, suggesting the possibility that need-free salt intake might be linked to modification (down-regulation) of the inhibitory tachykininergic system.