Neuropeptide K stimulates corticosterone release in the rat

We have investigated the effects of the tachykinin, neurokinin A (NKA) and N-terminally extended forms NPK and NP gamma on plasma levels of corticosterone. Both peripheral and central injections of these three NK-2 receptor agonists stimulated adrenal corticosterone release in gonad-intact and castrated male rats. A comparison of their effects revealed that NPK was relatively more potent than NKA and NP gamma. These results suggest that tachykinins may act at both central and peripheral sites to stimulate corticosterone release and that NKA and NP gamma may represent degradation forms of the larger, biologically effective tachykinin, NPK.