Adrenalectomy decreases neuropeptide Y mRNA levels in the arcuate nucleus

Recent studies suggest that glucocorticoids may increase NPY and NPY mRNA levels. To determine if endogenous corticosterone affects the level of NPY mRNA in areas that control NPY levels in the paraventricular nucleus, we examined the effects of adrenalectomy and corticosterone replacement on NPY mRNA levels in the arcuate nucleus and brainstem. Rats were either adrenalectomized, adrenalectomized and corticosterone replaced, or sham-operated. The arcuate nucleus, hypothalamus (excluding arcuate nucleus), and brainstem were collected and the RNA isolated. Dot blots were made of each tissue and the NPY mRNA quantitated by densitometry. Adrenalectomy significantly reduced NPY mRNA levels in the arcuate nucleus, while corticosterone replacement restored the NPY mRNA levels. NPY mRNA levels in the remainder of the hypothalamus were not affected by adrenalectomy. Adrenalectomy also had no affect on NPY mRNA levels in the brainstem. These data suggest that the paraventricular nucleus may be affected by glucocorticoids via an NPY pathway and that the two major afferent pathways of NPY-containing neurons to the paraventricular nucleus may be regulated by different mechanisms.