Department of Physiological Sciences, Federal University of Espírito Santo, Vitória-ES, Brazil.
Psychoneuroendocrinology. 2010 Feb;35(2):262-71. doi: 10.1016/j.psyneuen.2009.06.021. Epub 2009 Jul 23.
Stimulation of the dorsal periaqueductal gray matter (DPAG) produces defensive behaviors which are reminiscent of panic attacks. Recent evidence from our laboratory showed that DPAG-evoked defensive behaviors are markedly attenuated in short-term methimazole-induced hypothyroidism. It is not clear, however, whether these effects were due to an increase in thyrotropin releasing hormone (TRH), a decrease in thyroid hormones or to the overall effects of hypothyroidism. Accordingly, here we examined whether the peripheral injection of TRH has any effect either on the panic-like behaviors induced by electrical stimulation of DPAG or anxiety-like behaviors of rats exposed to the elevated plus-maze (EPM). Rats whose stimulation of DPAG produced flight responses (galloping or jumping) with intensities below 60 microA were injected with 1 microg/kg TRH (i.p.) and stimulated 10min after that. The day after, rats were treated with saline and subjected to the same stimulation procedure. Threshold curves were fitted through the logistic model and compared by likelihood-ratio chi(2) tests. TRH and saline effects on EPM performance were appraised in separate groups. Compared to saline-sessions, TRH-injected rats presented thresholds significantly higher for immobility (40%), trotting (33%), galloping (34%), jumping (39%) and exophthalmus (43%). In contrast, TRH had no effects on EPM arm exploration. TRH selective inhibition of DPAG-evoked defensive behaviors adds new evidence that panic attacks may be attenuated by increased levels of this hormone in hypothyroidism.
刺激背侧导水管周围灰质（DPAG）会产生防御行为，这些行为让人联想到恐慌发作。我们实验室的最新证据表明，在短期甲巯咪唑诱导的甲状腺功能减退症中，DPAG 诱发的防御行为明显减弱。然而，目前尚不清楚这些影响是由于促甲状腺激素释放激素（TRH）增加、甲状腺激素减少还是甲状腺功能减退症的整体影响所致。因此，在这里我们研究了外周注射 TRH 是否会对 DPAG 电刺激引起的类似恐慌的行为或暴露于高架十字迷宫（EPM）的大鼠的焦虑样行为产生任何影响。DPAG 刺激产生的逃避反应（奔跑或跳跃）强度低于 60μA 的大鼠，腹腔注射 1μg/kg TRH（i.p.），并在 10 分钟后进行刺激。第二天，大鼠用生理盐水处理，并进行相同的刺激程序。通过逻辑模型拟合阈值曲线，并通过似然比卡方检验进行比较。在单独的组中评估 TRH 和盐水对 EPM 性能的影响。与生理盐水组相比，TRH 注射大鼠的不动（40%）、小跑（33%）、奔跑（34%）、跳跃（39%）和眼球突出（43%）的阈值显著升高。相比之下，TRH 对 EPM 臂探索没有影响。TRH 对 DPAG 诱发防御行为的选择性抑制增加了新的证据，表明甲状腺功能减退症中这种激素水平的增加可能会减轻恐慌发作。
