Effects of pituitary hormonal treatment on responsiveness of anterior preoptic neurons in male leopard frogs,Rana pipiens

Abstract

Responses of units in the anterior part of the preoptic nucleus (APON) to con-specific or hetero-specific mating calls were studied in intact, saline-injected or pituitary-injected leopard frogs,Rana pipiens. 1. Electrical activity of many APON units was excited by auditory stimulation through play-back ofR. pipiens mating calls. There were three different response patterns: on-phasic, on-tonic, and gradual incremental increase of discharges after a relatively long latency. A small number of APON units was suppressed by the con-specific mating call. 2. Injections of pituitary homogenate significantly increased the percentage of APON units excited byR. pipiens mating calls. 3. Playback of hetero-specific mating calls ofR. catesbeiana orR. nigromaculata was frequently stimulatory or inhibitory for APON units which were responsive to con-specific mating calls. Mating calls ofR. japonica orHyla arborea had little or no influence on unitary activity in the APON. Electrical activity of units indifferent toR. pipiens mating calls also was not affected by hetero-specific mating calls. 4. The excitation of APON neurons by con-specific mating calls indicates that they may play an important role in evocation of chorusing mate calling behavior in maleR. pipiens.