Glucocorticoid inhibition of stress-induced changes in hypothalamic corticotrophin-releasing factor messenger RNA and proenkephalin A messenger RNA.

We have examined the effects of localised administration of the synthetic glucocorticoid dexamethasone on basal and stress-induced levels of mRNA for both corticotrophin-releasing factor (CRF) and proenkephalin A, in parvocellular neurons of the paraventricular nucleus (PVN). Unilateral implants of cholesterol directly over the PVN had no effect on either basal or stress-induced increase of CRF and proenkephalin A message. However, unilateral implants of dexamethasone significantly decreased basal CRF mRNA compared to the contralateral, unimplanted side and prevented the increase in CRF and proenkephalin A mRNA 4 hours after ip hypertonic saline stress. These findings confirm the PVN as a site for glucocorticoid feedback. Furthermore the data demonstrates a steroid-sensitive stress mediated increase in proenkephalin A mRNA which provides additional evidence for a role of the endogenous opiates in the hypothalamic neuroendocrine response to stress.