Release of oxytocin and vasopressin by magnocellular nuclei in vitro: specific facilitatory effect of oxytocin on its own release.

The release of endogenous oxytocin and vasopressin by rat paraventricular and supraoptic nuclei in vitro during a 10-min period, 30 min after beginning the incubation, was measured radioimmunologically. Mean basal hormone release per 10 min and per pair of nuclei was: 128.4 +/- 12.

The vasotocin-like biological activity present in the bovine pineal is due to a compound different from vasotocin.

The vasotocin-like biological activity detected in an extract (E5 fraction) of bovine pineal gland was found not to be due to the presence of vasotocin, vasopressin or oxytocin. The data obtained by means of bio- and radioimmunoassays suggest that the peptide responsible for this biological activity, however, possess the same Pro-Arg-Gly(NH2) tripeptidic carboxy-terminal end as vasotocin.