Glucoprivation-Induced Fos Expression in the Hypothalamus and Medulla Oblongata in Female Rats

Abstract

Glucoprivation induced by 2-deoxy-D-glucose (2DG) suppresses pulsatile luteinizing hormone (LH) secretion in female rats. The suppression is enhanced in the presence of estrogen. In the present study, 2DG-induced Fos expression was examined in the solitary tract nucleus (NTS), hypothalamic paraventricular nucleus (PVN), raphe obscurus nucleus (ROb) and raphe pallidus nucleus (RPa), which have been previously suggested to be involved in glucoprivation-induced suppression of LH secretion in female rats. Ovariectomized (OVX) or estrogen-primed ovariectomized (OVX+E₂) rats were injected intravenously with 2DG (400 mg/kg BW). The brain was removed 1 h after the injection. The number of Fos-like-immunoreactive (Fos-li) cells in the PVN and NTS was significantly increased in OVX+E₂ rats compared with control groups, but did not show a significant increase in the OVX group. Few Fos-li cells were observed in the ROb and RPa in all groups. All of the Fos-li cells in the PVN and NTS were neurons because they had immunoreactivities to microtubule-associated protein 2. Some Fos-li cells (8.3%) had tyrosine hydroxylase-like immunoreactivities in the NTS in 2DG-treated OVX+E₂ rats. These results suggest that neurons in the PVN and NTS are involved in the estrogen-dependent neural cascade mediating glucoprivic suppression of LH secretion in female rats.