Young E A, Akil H
Endocrinology. 1985 Jul;117(1):23-30. doi: 10.1210/endo-117-1-23.
The effects of acute and chronic stress on the release of ACTH and beta-endorphin in response to stimulation by ovine corticotropin-releasing factor (CRF) and arginine vasopressin were examined. Pituitaries were removed from rats who had received either acute stress, chronic stress daily for 14 days with the last stress occurring 24 h before decapitation, or chronic stress followed by an acute stress immediately before decapitation (chronic stress-acute stress). Pituitaries from naive unstressed animals were used as the control group. After processing into single cell suspensions, the pituitaries were incubated with various doses of CRF (10(-11) M to 10(-9) M) and AVP (10(-10) M to 10(-8) M). Release of ACTH and beta-endorphin into the medium was measured by RIA. A clear dose-dependent response to both releasers was seen in control pituitaries. In acute stress, a decreased responsiveness to arginine vasopressin and CRF was seen. This same blunted response was not seen in chronic stress even if the animals are stressed immediately before decapitation. At higher doses of CRF (10(-9) M) a substantially increased release of ACTH and beta-endorphin was seen in the chronically stressed rats. When the content of the anterior pituitary lobe was assayed in these animals, both chronic stress groups show increased content of ACTH and beta-endorphin, which may indicate an increase amount of ACTH and beta-endorphin in the releasable pools in chronic stress. In addition, the failure of further stress to alter the response to CRF in the chronic stress-acute stress group may indicate a down-regulation of the steroid feedback on the pituitary. However, it is clear that no down-regulation of the CRF receptor occurs in this chronic stress paradigm.
研究了急性和慢性应激对大鼠垂体促肾上腺皮质激素（ACTH）和β-内啡肽释放的影响，这些大鼠垂体对绵羊促肾上腺皮质激素释放因子（CRF）和精氨酸加压素（AVP）刺激的反应。从接受过急性应激、连续14天每日接受慢性应激（最后一次应激发生在断头前24小时）或在断头前立即接受慢性应激后再进行急性应激（慢性应激-急性应激）的大鼠中取出垂体。从未经应激的正常动物的垂体用作对照组。将垂体处理成单细胞悬液后，与不同剂量的CRF（10⁻¹¹ M至10⁻⁹ M）和AVP（10⁻¹⁰ M至10⁻⁸ M）一起孵育。通过放射免疫分析法（RIA）测量培养基中ACTH和β-内啡肽的释放。对照组垂体对两种释放因子均呈现明显的剂量依赖性反应。在急性应激组中，对精氨酸加压素和CRF的反应性降低。即使动物在断头前立即受到应激，慢性应激组也未出现这种反应迟钝的情况。在较高剂量的CRF（10⁻⁹ M）时，慢性应激大鼠中ACTH和β-内啡肽的释放显著增加。当检测这些动物垂体前叶的含量时，两个慢性应激组的ACTH和β-内啡肽含量均增加，这可能表明慢性应激时可释放池中ACTH和β-内啡肽的量增加。此外，在慢性应激-急性应激组中，进一步的应激未能改变对CRF的反应，这可能表明垂体上类固醇反馈的下调。然而，很明显在这种慢性应激模式下CRF受体未发生下调。
