Stimuli mediated by female pheromones reach the brain through the vomeronasal organ, and are forwarded to the medial nucleus of the amygdala (MeA) through the accessory olfactory bulb. Neurons of the MeA project to the ventral premamillary nucleus (VPM) regulating GNRH expression in the preoptic area whereby they act on LH secretion of the pituitary, necessary for correct reproductive function of males.

We have demonstrated expression of nesfatin-1/NUCB2-t (nesfatin) mRNA and protein in majority of the VPM cells. Our goal was to study whether these neurons are activated by female odors evoked stimuli in males. Additionally, we aimed to identify specific conditions that may modify this activation, and to characterize cells trough which this modification can be realized. Therefore, we performed a female odor test on adult sexually inexperienced male rats and analyzed activation (Fos immunoreactivity) of nesfatin-positive neurons in the VPM. Since urocortin3 (URC3) containing fibers originated mainly from the MeA form a dense network in the VPM, but they function is unclear, we also investigated possible connections between nesfatin-positive neurons and URC3-immunoreactive terminals. To reveal what type of stimuli may be mediated by URC3 to the VPM, we subjected rats either to restraint stress or hypoglycemia.

Female odor test resulted in an activation of 24 ± 7 % of nesfatin neurons in the VPM (n=4). Many of nesfatin-positive neurons formed close contacts with URC3 positive terminals. Subpopulation of the URC3-immunoreactive cells was activated by hypoglycemia, but not by restraint stress.

Our results suggest that nesfatin containing neurons in the VPM of male rats may participate in mediation of endocrine responses evoked by female pheromones. URC3-positive cells in the MeA may convey information about the low blood glucose level to the VPM, and they may modify the functional activity of VPM neurons.

Supported by: OTKA CK80180