Neuroendocrine effects of some amphibian peptides.

The effect of dermorphin and sauvagine, two new peptides originally isolated from amphibian skin, on the release of gonadotropins and prolactin was studied "in vivo" and "in vitro." The intraventricular administration of dermorphin to castrated male rats induces a significant decrease in serum LH, but not FSH, levels. Subcutaneous, as well as intraventricular, injections of dermorphin to normal male rats induce a statistically significant increase in serum prolactin levels, which is counteracted by naloxone. In the isolated and dispersed rat pituitary cell preparation, the addition of dermorphin to the media does not induce any alteration in prolactin output. Intraventricular administrations of sauvagine are ineffective in influencing the secretion of both LH and FSH. This peptide is also unable to modify it when tested "in vitro". On the contrary, subcutaneous injections of sauvagine to either normal male or lactating rats decrease serum prolactin levels. This prolactin inhibitory effect is also present "in vitro." These results suggest that dermorphin and sauvagine modulate the secretory activity of the anterior pituitary gland. However, the mechanism of control is different: dermorphin needs the mediation of brain structures, while sauvagine acts directly at the pituitary level.