Effects of estradiol on glucoprivic transactivation of catecholaminergic neurons in the female rat caudal brainstem

Hyperphagic and hypothalamic neuroendocrine responses to acute glucose depr ivation are modified by the ovarian steroid estradiol (E). Observations of genomic activation of catecholaminergic (CA) neurons in the hindbrain later al reticular nucleus, nucleus of the solitary tract, and area postrema (AP) by glucopenia support their potential function in pathways mediating regul atory effects of this metabolic challenge within the brain. Expression of E receptors by these cells suggests that their activity may be sensitive to steroid modulation during glucopenia. The present studies investigated the role of E on transcriptional activation of caudal brainstem CA neurons by t he glucose antimetabolite, 2-deoxy-D-glucose (2DG). Ovariectomized rats wer e implanted with s.c. Silastic capsules containing E (30 or 250 mug/ml) or sesame oil, and injected i.p. 7 days later with 400 mg 2DG/kg or saline. Ty rosine hydroxy[ase (TH)-immunore-active (-ir) neurons in the C-1/A(1), C-2, C-3, A(2), A(5), and A(6) cell groups and AP were colabeled for Fos follow ing antimetabolite administration, whereas vehicle injection resulted in ne gligible nuclear staining of these cells. With the exception of A(2), A(6), and AP cells, mean numbers of Fos- and TH-/Fos-ir-positive neurons in thes e brain sites did not differ between E- and sesame oil-implanted groups. Nu mbers of TH-positive A(2) and A(6) neurons that expressed Fos in response t o 2DG were significantly greater in rats implanted with the high E dose vs. either the low steroid dose or sesame oil. These results show that the mag nitude of cellular Fos labeling within discrete hindbrain CA neuron populat ions varies in accordance with circulating E levels. These findings suggest that E may exert potential modulatory effects on glucoprivic activation of the Fos stimulus/transcription cascade and consequent compensatory genomic responses within specific areas of the female rat caudal brainstem. Copyri ght (C) 2001 S. Karger AG, Basel.