NK-1 TACHYKININ RECEPTOR IN RAT AND GUINEA-PIG BRAINS - PHARMACOLOGICAL AND AUTORADIOGRAPHICAL EVIDENCE FOR A SPECIES-DIFFERENCE

The affinities of a large variety of peptide or nonpeptide tachykinin analogues were determined on membranes from rat and guinea pig brains using the selective NK-1 radioligand H-3-[Pro9]SP. Nonpeptide antagoni sts clearly revealed a species difference; (+/-)CP-96,345 was more pot ent in the guinea pig, while RP 67580 was found to be a better competi tor of H-3-[Pro9]SP binding to rat brain membranes. This was confirmed on brain slices by autoradiography. Numerous brain structures were an alyzed by optical densitometry. From these data, a heterogeneity of NK -1 binding sites among different structures can be excluded in both ra t and guinea pig brains.