Sex Difference and Testosterone Modulation of Pheromone-Induced Neuronal Fos in the Ferret’s Main Olfactory Bulb and Hypothalamus(3)

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The relatively small size of the ferret’s VNO-AOB system raises the question of whether it is activated by pheromones. When gonadally intact, breeding male and female ferrets were either allowed to mate or exposed to odors from breeding animals of the opposite sex, significant increases in neuronal Fos-IR were seen in the granule cell layer of the MOB but not in the AOB. Female subjects showed a significant induction of neuronal Fos-IR in central segments of the chemosensory pathway (i.e., mPOA and VLH) in response to male odors, whereas male subjects showed no such response to female odors. The absence of any odor-induced neuronal Fos response in the AOB does not definitively prove that this system is unresponsive to pheromonal signals. The presence of increased neuronal Fos-IR in the MOB suggests, however, that the main olfactory system is activated by pheromones. The observed odor-induced increments in neuronal Fos-IR in the MA (both sexes), and in the BNST, VLH, and mPOA (females only) further suggest that these main olfactory inputs are conveyed to the hypothalamus, at least in females. buy cipro

In our previous study, we observed a sex difference in hypothalamic Fos responses to different pheromones. In experiment 1 of the present study, we systematically compared the ability of pheromones from the same source (soiled estrous female bedding) as well as a nonpheromonal odor, artificial peppermint, to augment neuronal Fos-IR throughout the chemosensory pathway to the hypothalamus in male and female ferrets.