Biogenic amines and beta-endorphin responses in the rat vas deferens.

1. Recent studies have demonstrated that activation of opioid peptide receptor by beta-endorphin results in a change of bioamines in peripheral tissues. 2. The present results could be interpreted assuming that the action of beta-endorphin, on the smooth muscle of the isolated rat vas deferens, is independent of catecholaminergic, cholinergic and tryptaminergic neurotransmission. 3. There is evidence that it is through a specific opioid 'epsilon-receptor' which have been shown a high degree of affinity for beta-endorphin.