Pisarska M, Mulchahey J J, Welge J A, Geracioti T D, Kasckow J W
Cincinnati VAMC, Cincinnati, OH 45267, USA.
Brain Res. 2000 Sep 22;877(2):184-90. doi: 10.1016/s0006-8993(00)02606-8.
Corticotropin-releasing factor (CRF) coordinates the mammalian response to stress. In the amygdala, the CRF system appears to be responsible, at least in part, for the behavioral responses resulting from stress. Associated with amygdalar CRF is a 37 kDa binding protein (CRF-BP) which may also play a role in regulating stressful stimuli. Aging has been shown to be associated with abnormal neuroendocrine stress systems and little is known with regards to how amygdalar stress systems change with aging. In our study, we have assessed levels of amygdalar CRF and CRF-BP mRNA in Fischer 344 rats of 4, 12 or 24 months of age following 14 days of hourly restraint. Prior to sacrifice, rats were also tested for anxiety-like behaviors on the elevated plus maze. After behavioral testing, rats were perfused with 4% paraformaldehyde and the brains were processed for in situ hybridization. Twenty micron sections were hybridized with a CRF as well as a CRF-BP riboprobe. Following hybridization, tissue sections were oppossed to X-ray film and relative amounts of mRNA in the amygdala were quantitated. Levels of CRF mRNA in the amygdala of 12 and 24 month-old rats following chronic restraint were significantly lower relative to rats which were handled for 14 days. There were no significant differences in amygdalar CRF gene expression between stressed and handled 4 month-old rats. At 12 and 24 months of age but not 4 months, there were also significant effects of restraint associated with decreases in amygdalar CRF-BP gene expression. Furthermore, there were reciprocal decreases in anxiety-like behaviors in the 12 and 24 month-old rats which were significant; the changes in anxiety-like behaviors between restrained vs. handled 4 month-old rats were not significantly different. The decreased gene expression of CRF in the amygdala in concert with decreased anxiety-like behaviors following restraint is consistent with the known behavioral effects of exogenously applied intra-amygdalar CRF. The changes in amygdalar CRF-BP observed may be secondary to the known regulatory effects that CRF exhibits on its binding-protein. These studies have relevance to better understanding the molecular basis of aging related changes in neuroendocrine stress systems.
促肾上腺皮质激素释放因子（CRF）协调哺乳动物对压力的反应。在杏仁核中，CRF系统似乎至少部分地负责由压力引起的行为反应。与杏仁核CRF相关的是一种37 kDa的结合蛋白（CRF-BP），它也可能在调节应激刺激中发挥作用。衰老已被证明与异常的神经内分泌应激系统有关，而关于杏仁核应激系统如何随衰老而变化知之甚少。在我们的研究中，我们评估了在每小时进行14天束缚后，4、12或24月龄的Fischer 344大鼠杏仁核中CRF和CRF-BP mRNA的水平。在处死前，还在高架十字迷宫上对大鼠进行了焦虑样行为测试。行为测试后，用4%多聚甲醛灌注大鼠，然后对大脑进行原位杂交处理。用CRF以及CRF-BP核糖探针与20微米厚的切片杂交。杂交后，将组织切片与X光片相对放置，定量杏仁核中mRNA的相对含量。与处理14天的大鼠相比，慢性束缚后12和24月龄大鼠杏仁核中CRF mRNA的水平显著降低。在应激和处理过的4月龄大鼠之间，杏仁核CRF基因表达没有显著差异。在12和24月龄而非4月龄时，束缚也对杏仁核CRF-BP基因表达的降低有显著影响。此外，12和24月龄大鼠的焦虑样行为有显著的相互降低；束缚与处理过的4月龄大鼠之间焦虑样行为的变化没有显著差异。束缚后杏仁核中CRF基因表达的降低与焦虑样行为的减少相一致，这与外源性杏仁核内注射CRF已知的行为效应相符。观察到的杏仁核CRF-BP的变化可能是CRF对其结合蛋白所表现出的已知调节作用的继发结果。这些研究对于更好地理解神经内分泌应激系统中与衰老相关变化的分子基础具有重要意义。
