A selective tachykinin receptor agonist promotes differentiation but not survival of rat chromaffin cells in vitro.

Rat chromaffin cells display phenotypic plasticity postnatally. In the presence of glucocorticoids, they retain a chromaffin cell phenotype, whilst in the presence of nerve growth factor and the absence of glucocorticoids they adopt a sympathetic neuronal phenotype. The tachykinins have some of the characteristics of a neurotrophic factor and are present in the form of a substance P afferent input in the rat adrenal medulla. We investigated the effects of stable NK1 and NK2 tachykinin receptor agonists, Ava[L-Pro,N-Me-Leu-10]SP7-11 (GR73632) and [Lys-3,Gly-8,R-Lac-Leu-9]NKA3-10 (GR64349), respectively, on the survival and phenotype of P5-7 rat chromaffin cells in vitro. GR73632 promoted neurite outgrowth, characteristic of the sympathetic neuronal phenotype, in the absence of NGF and glucocorticoids, but was without effect on survival after 2 weeks in culture. GR64349 was without effect.