Neuronal activity in the mediobasal hypothalamus of hibernating jerboas (Jaculus orientalis)

The expression of the c-fos protein in the mediobasal hypothalamus (MBH) of the jerboa was examined both during hibernation and on arousal from hibernation. Expression was examined by c-fos immunohistochemistry using a polyclonal antibody raised against c-fos protein. In jerboas hibernating for 2 days, a significant number of c-fos immunopositive neurons were found in the median eminence and ventrolateral arcuate nucleus. Such an immunoreaction was not observed in non hibernating control animals. In animals hibernating for 10 days, c-fos immunoreactivity was localized in the lateral arcuate nucleus and ventromedial hypothalamus (VMH), the median eminence displayed no immunoreaction. After arousal from hibernation, the fos immunoexpression within the MBH was exclusively limited to the VMH nucleus. Thus, the present study shows different patterns of c-fos protein expression during hibernation, notably in the neuroendocrine systems of MBH. Consequently, the mediobasal hypothalamus seems to be implicated in a physiological regulation during hibernation. Moreover, the present data suggest that the c-fos gene is either implicated in mediating or is a consequence of physiological activation of specific neuron systems of the desert jerboa.