TACHYKININ RECEPTORS IN THE RAT ISOLATED UTERUS

Tachykinin receptors mediating uterotonic effects were examined in pre parations from oestrogen-primed rats. In the absence of peptidase inhi bitors [Lys5-MeLeu9-Nle10] NKA (4-10) was 14-fold more potent than neu rokinin A (NKA), but the two peptides were equipotent in the presence of phosphoramidon alone and in combination with amastatin. The NK-2 re ceptor antagonist SR 48968 antagonised responses to the tachykinins. T hese findings indicate that an NK-2 receptor is present in the oestrog en-primed rat uterus and that endopeptidase 24.11 plays a major role t o inactivate NKA in this tissue.