Control of salt intake by steroids and cerebral peptides.

Steroids (aldosterone and testosterone) and peptides of cerebral origin (angiotensin II and the tachykinins) control the salt intake of the rat. They arouse or suppress the behaviour and produce life-long enhancements of NaCl intake. Need-induced salt intake (salt appetite or salt hunger), which is the consequence of sodium deficiency, is aroused by a synergy within the brain of cerebral angiotensin II and aldosterone. And prior episodes of sodium depletion produce enhancements of subsequent salt appetites, but only if the prior depletions were accompanied by angiotensin II and aldosterone action. Need-free salt intake, which occurs daily when the rat is in positive sodium balance, is inherently high in the rat and is organized in the perinatal period by aromatized testosterone which suppresses the intake of the male. It is also enhanced by prior activations of angiotensin II and aldosterone. Both need-induced and need-free salt intake are suppressed by intracranial tachykinins. Non-mammalian tachykinins (eledoisin, physalaemin, kassinin) are both antidipsogenic and antinatriorexigenic, but amino-senktide, an analogue of the mammalian tachykinin substance P with selective affinity for the NK 3 receptor, appears to be a selective antinatriorexigenic agent, and could provide a rational therapy for chronic overconsumption of salt.