Medial preoptic area dopaminergic responses to female pheromones develop during puberty in the male Syrian hamster.

Chemosensory cues from receptive females do not elicit similar reactions before and after puberty in male hamsters. While pheromones facilitate a complex display of reproductive behavior in adults, prepubertal males do not engage in these same behaviors. Dopamine (DA) released from the medial preoptic area (MPOA) in response to a receptive female or her odors is an important component of the neural events underlying adult male rat sexual behavior. The current experiment investigated whether increased dopaminergic activity occurs in the adult male hamster MPOA in response to female pheromones, and if so, whether this response is absent in prepubertal males, which do not mate. Sexually nai;ve prepubertal and adult male hamsters were exposed to cotton swabs with or without pheromone from an estrous female for 0, 5, 15, or 25 min, after which brains were collected and frozen on dry ice. The MPOA was micropunched from frozen coronal sections (500 microm), and concentrations of DA and its primary metabolite DOPAC were determined by high-performance liquid chromatography-electrochemical detection. DOPAC was used as an index of dopaminergic activity. DOPAC levels significantly increased in adults after 15 min exposure to pheromone. In contrast, MPOA DOPAC concentrations did not increase in prepubertal males exposed to pheromone. These data demonstrate that the neural processing of sexually relevant chemosensory stimuli matures during puberty. The absence of a DA response to female pheromones prior to puberty may contribute to the inability of prepubertal males to display reproductive behavior.