Marin Marcelo T, Cruz Fabio C, Planeta Cleopatra S
Laboratory of Pharmacology, School of Pharmaceutical Sciences, UNESP-São Paulo State University, Rod. Araraquara-Jaú Km 1, 14801-902, Araraquara, São Paulo, Brazil.
Physiol Behav. 2007 Jan 30;90(1):29-35. doi: 10.1016/j.physbeh.2006.08.021. Epub 2006 Oct 4.
Organisms are constantly subjected to stressful stimuli that affect numerous physiological processes and activate the hypothalamo-pituitary-adrenal (HPA) axis, increasing the release of glucocorticoids. Exposure to chronic stress is known to alter basic mechanisms of the stress response. The purpose of the present study was to compare the effect of two different stress paradigms (chronic restraint or variable stress) on behavioral and corticosterone release to a subsequent exposure to stressors. Considering that the HPA axis might respond differently when it is challenged with a novel or a familiar stressor we investigated the changes in the corticosterone levels following the exposure to two stressors: restraint (familiar stress) or forced novelty (novel stress). The changes in the behavioral response were evaluated by measuring the locomotor response to a novel environment. In addition, we examined changes in body, adrenals, and thymus weights in response to the chronic paradigms. Our results showed that exposure to chronic variable stress increased basal plasma corticosterone levels and that both, chronic restraint and variable stresses, promote higher corticosterone levels in response to a novel environment, but not to a challenge restraint stress, as compared to the control (non-stressed) group. Exposure to chronic restraint leads to increased novelty-induced locomotor activity. Furthermore, only the exposure to variable stress reduced body weights. In conclusion, the present results provide additional evidence on how chronic stress affects the organism physiology and point to the importance of the chronic paradigm and challenge stress on the behavioral and hormonal adaptations induced by chronic stress.
生物体不断受到应激刺激，这些刺激会影响众多生理过程并激活下丘脑 - 垂体 - 肾上腺（HPA）轴，从而增加糖皮质激素的释放。已知长期暴露于慢性应激会改变应激反应的基本机制。本研究的目的是比较两种不同应激模式（慢性束缚或可变应激）对行为和皮质酮释放的影响，以及随后暴露于应激源时的情况。考虑到当HPA轴受到新的或熟悉的应激源挑战时可能会有不同反应，我们研究了暴露于两种应激源（束缚，熟悉的应激；或强迫新奇，新的应激）后皮质酮水平的变化。通过测量对新环境的运动反应来评估行为反应的变化。此外，我们检查了慢性应激模式下身体、肾上腺和胸腺重量的变化。我们的结果表明，暴露于慢性可变应激会增加基础血浆皮质酮水平，并且与对照组（无应激组）相比，慢性束缚和可变应激都会使对新环境而非束缚应激挑战产生更高的皮质酮水平。暴露于慢性束缚会导致新奇诱导的运动活动增加。此外，只有暴露于可变应激会导致体重减轻。总之，本研究结果为慢性应激如何影响生物体生理提供了更多证据，并指出了慢性应激模式和应激挑战在慢性应激诱导的行为和激素适应方面的重要性。
