Meeting Abstract
Sexually dimorphic behaviors are useful systems in which to study the role of hormones in generating behavioral diversity within a species. The mating calls of Xenopus laevis are sexually distinct; female calls are slow and monophasic, while male calls are faster and biphasic. The circuit that produces these vocalizations is a central pattern generator consisting of androgen sensitive premotor and motor nuclei. The production of male song requires circulating androgens; gonadectomized male song degrades, while androgen-treated females (T-females) develop the ability to produce male-like calls. We used whole-cell electrophysiology to investigate the vocal circuit changes underlying the masculinization of T-female vocal behavior. We identified premotor neurons in T-females with vocal activity during song resembling that of male premotor vocal cells. These cells increased in size over the course of testosterone treatment, reaching male-like values after 8 weeks of androgen exposure; they also possessed the hyperpolarization activated cation current, IH, and displayed NMDA receptor-dependent oscillations, both of which are characteristic of male premotor cells. In males, vocal cells in the premotor nucleus can be categorized into two groups based on differences in activity during song. T-female vocal neurons also separated into these two groups when compared with male cells. Both cell types were found throughout the course of androgen treatment. Our findings suggest that the masculinization of vocal behavior involves changes to cell morphology and intrinsic currents in the premotor nucleus, and involves both premotor cell types.
