The blood pressure changes resulting from the microinjection of fragments of the beta endorphin molecule into the nucleus tractus solitarii (NTS).

Unilateral microinjection of gamma endorphin (1-17) into the nucleus tractus solitarii (NTS) of the urethane anaesthetised rat produces a dose-related pressor response. This effect has been examined in the present study, by means of fragments of the molecule. Unilateral application of the peptides 6-16, 10-16, 6-17 and 10-17 (1 ng) all produced an equivalent rise in blood pressure, however the time course of 6-16 and 10-16 was more rapid than that of gamma endorphin or the fragments containing the 17th amino acid. Naloxone (10 ng) administered into the NTS, did not affect the maximum rise in pressure induced by 6-17 (1 ng). It is concluded that in addition to a depressor region, which is dependent on the N-terminal tyrosine, the beta endorphin molecule (1-31) also has a pressor region, which is present within the amino acid sequence 10-16, and is a non-opiate effect.