Intracranial aminosenktide blocks renin-induced sodium appetite in the rat neonate

Sodium hunger in rats can be evoked by activation of brain renin-angiotensin as early as 72 h postnatally. In adults sodium hunger is inhibited by intracranial injection (pICV) of tackykinins, but it is not known whether this occurs in the early postnatal period. We stimulated sodium hunger in 72-h-old rat neonates with renin (100 ng, pICV) and tested the effect of the NK3 agonist aminosenktide (AS, 100 ng, pICV) on the appetite. AS blocked the renin-enhanced intake of orally infused 6% NaCl while leaving water intake unaffected. The effect is specific to salt and not fluids since in a second experiment AS blocked renin-enhanced licking of solid NaCl. These results show that aminosenktide inhibits salt hunger before it can be expressed in response to sodium depletion at 12 days-of-age, which AS suppresses in adults. Thus, in addition to brain angiotensin, the tachykinin substrates that mediate salt appetite in medial amygdala and stria terminalis are functional 72 h postnatally in the rat.