Sex Differences During Development in NeuN Labeling of the MPN mag of Syrian Hamsters
Holly Richendrfer, Jennifer Swann
Sexual behavior is critical for ensuring the survival of many species. To date, male sex behavior in all vertebrate species is regulated by the medial preoptic area (MPOA). In the Syrian hamster, male mating behavior is regulated by a subdivision of the MPOA, the magnocellular division of the medial preoptic nucleus (MPNmag). Lesions of the MPNmag eliminate male mating behavior. Adult males have significantly greater number and density of neurons in this nucleus compared to females. Our lab has shown that the MPN mag becomes sexually dimorphic in the total number of cells between postnatal days 5 and 10. Yet, it is not known whether these differences in cell number reflect differences in neuron number or another cell type. NeuN is a protein found exclusively in neurons. The goal of this experiment was to determine if there is a sex difference in the number of neurons in the MPN mag on postnatal day 5 or 10 by examining the number of NeuN labeled cells in the MPN mag.
Male and female hamsters were perfused 5 or 10 days after birth. Brains were removed, cut into 40 um sections on a freezing microtome, mounted on slides and stored at -20C until labeled for NeuN using immunocytochemistry. The number of neurons was determined using the particle counting program in ImageJ. Our data suggests that sex differences in neuron number are present as early as postnatal day 5.