Gonadectomy reduces the concentrations of putative receptors for arginine vasotocin in the brain of an amphibian.

Putative receptors for arginine vasotocin (AVT) in the brain of the newt (Taricha granulosa) were measured using quantitative autoradiography with tritium-labelled vasopressin. Specific binding sites were observed in the olfactory bulb, medial (hippocampal) pallium, dorsal pallium, amygdala para lateralis and tegmental region of the medulla oblongata. In both male and female newts, concentrations of binding sites in the amygdala, but not in the other four areas, were significantly lower in gonadectomized animals than in sham-operated controls. The equilibrium dissociation constants (KdS) were not altered by gonadectomy. Since long-tem castration abolishes the effect of AVT injection on sexual behaviors, these results support the hypothesis that gonadal steroids maintain sexual behaviors in this amphibian by maintaining AVT receptors in the amygdala.