Abstract
In breeding season, the sexually mature male newt, Cynops pyrrhogaster, vibrates the tail in front of the female at an early stage of courtship. The effects of intracerebroventricular (ICV) and intraperitoneal (IP) injections of ovine prolactin (PRL), antiserum against newt PRL, and antibody against the newt PRL receptor on the expression of the tail-vibrating behavior of male newts were studied to see whether PRL acts centrally or peripherally to induce the behavior. Both of ICV and IP injections of PRL to gonadotoropin-primed males enhanced the expression of the behavior dose-dependently. The minimum effective dose of PRL was 0.1 μg for ICV injection, whereas it was 100 μg for IP injection. The minimum effective amount of the antiserum was 0.05 μl for ICV injection, whereas it was 20 μl for IP injection. Neither ICV nor IP injection of preimmune rabbit serum affected the expression of the behavior. Furthermore, ICV, but not IP, administration of 0.3 μg of anti-newt PRL receptor antibody blocked the spontaneously occurring courtship behavior in sexually developed males. Neither ICV nor IP injection of the same amount of normal rabbit IgG affected the expression of the behavior. These results strongly suggest that endogenous PRL enhances the behavior by acting centrally through the PRL receptors localized in the brain area. [J Physiol Sci. 2006;56 Suppl:S219]
