Plasma CRH Response to Water Immersion-Restraint Stress in Rats Bearing a Hypothalamic Knife Cut.
Access this Article
We reported earlier that the plasma level of corticotropin-releasing hormone (CRH) remained high 120min after the onset of such strong sustained stress as ether-laparotomy or water immersionrestraint, which reflected the persistent secretion of CRH from the hypothalamic median eminence (ME). We investigated the change in plasma CRH during water immersion-restraint stress in rats bearing an anterolateral cut around the medial basal hypothalamus (MBH) which cuts the CRH neurons from the PVN to the ME. Concentrations of CRH in the hypothalamus, extrahypothalamic tissues and peripheral blood were measured by radioimmunoassay. Plasma ACTH was measured with an immunoradiometric assay kit. Plasma baseline ACTH and CRH concentrations did not differ significantly in the sham vs. cut groups. At 120min after the onset of stress, plasma ACTH concentrations were definitely higher in both groups. In the cut group, plasma CRH at 120min after stress did not differ significantly from the baseline level, whereas plasma CRH at 120min was definitely higher in the sham group. Baseline CRH concentrations in the ME did not differ greatly in the two groups. CRH concentrations in the ME of both groups had decreased appreciably 120min after the onset of stress as compared with baseline CRH, and the CRH decrease was greater in the cut group than in the sham group. CRH in the neurointermediate lobe (NIL) and adrenal gland of both groups showed no significant change at 120min, compared with the control. These findings confirm that the continuous CRH increase in plasma during sustained stress is derived mainly from the hypothalamus. It is possible that the ACTH increase at 120min in the cut group depends not only on the secretion of pooled CRH in the ME but also on other ACTH-stimulating factors from peripheral tissues.
- Endocrine Journal
Endocrine Journal 41(4), 453-459, 1994
The Japan Endocrine Society