Pheromones from the mental glands of male plethodontid salamanders increase sexual receptivity in conspecific females. The pheromone enters the vomeronasal organ during courtship to produce this effect. Vomeronasal neurons from female Plethodon shermani were examined following exposure to male pheromone or saline placed on the nares. Agmatine was used in conjunction with the pheromone to enable immunocytochemical visualization of chemosensory neurons that were activated by the pheromone. Olfactory neurons exposed to pheromone or saline, and vomeronasal neurons exposed to saline did not demonstrate significant labeling. A population of vomeronasal neurons was intensely labeled following exposure to the pheromone. This study demonstrates that a specific population of vomeronasal neurons in a female plethodontid salamander is responsible for transmitting pheromonal information to the brain to produce modifications in behavior.

Conspecific pheromones can influence reproductive behaviors. The vomeronasal system plays an extensive role in the processing of pheromonal information. Male plethodontid salamanders utilize proteinaceous pheromones during courtship to increase the female's receptivity. In the present study, we have used neuronal uptake of agmatine as an indicator of the responsiveness of vomeronasal neurons in female plethodontid salamanders (Plethodon shermani) to male pheromones.

Whole pheromone extract from male mental gland or saline (each containing 3 mM AGB) was applied to female plethodon nares (n = 5 for each condition) for 45 minutes (2 microliter/2 min). Females were killed by decapitation and heads were fixed in 4% paraformaldehyde-2.5% glutaraldehyde overnight. Tissue was processed for cryostat sectioning (20 m), and standard immunocytochemical procedures were used to label AGB in tissue with DAB and Alexa 488. Labeled cells were mapped and counted throughout the entire vomeronasal organ.