[Alpha- and gamma-endorphin suppression of the chronotropic effects of exogenous acetylcholine].

On the isolated frog heart alpha- and gamma-endorphins depressed the chronotropic effects of exogenous acetylcholine. Naloxone partially blocked the atropine-like action of alpha-, gamma-endorphins. The latent period of the reaction to the endorphin injection was about 20 min, the endorphin effect retained more than 1 h. The obtained data show that some opioids may act as "endogenous atropine".