Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis, Indiana, USA.
Am J Physiol Regul Integr Comp Physiol. 2010 Jan;298(1):R130-40. doi: 10.1152/ajpregu.00574.2009. Epub 2009 Nov 18.
Previous studies suggest that sympathetic responses evoked from the preoptic area in anesthetized rats require activation of neurons in the dorsomedial hypothalamus. Disinhibition of neurons in the dorsomedial hypothalamus in conscious rats produces physiological and behavioral changes resembling those evoked by microinjection of muscimol, a GABA(A) receptor agonist and neuronal inhibitor, into the medial preoptic area. We tested the hypothesis that all of these effects evoked from the medial preoptic area are mediated through neurons in the dorsomedial hypothalamus by assessing the effect of bilateral microinjection of muscimol into the DMH on these changes. After injection of vehicle into the dorsomedial hypothalamus, injection of muscimol into the medial preoptic area elicited marked increases in heart rate, arterial pressure, body temperature, plasma ACTH, and locomotor activity and also increased c-Fos expression in the hypothalamic paraventricular nucleus, a region known to control the release of ACTH from the adenohypophysis. Prior bilateral microinjection of muscimol into the dorsomedial hypothalamus produced a modest depression of baseline heart rate and body temperature but completely abolished all changes evoked from the medial preoptic area. Microinjection of muscimol just anterior to the dorsomedial hypothalamus had no effect on autonomic and neuroendocrine changes evoked from the medial preoptic area. Thus, activity of neurons in the dorsomedial hypothalamus mediates a diverse array of physiological and behavioral responses elicited from the medial preoptic area, suggesting that the latter region represents an important source of inhibitory tone to key neurons in the dorsomedial hypothalamus.
先前的研究表明，麻醉大鼠前脑区诱发的交感反应需要激活下丘脑背内侧核的神经元。在清醒大鼠中，背内侧下丘脑神经元的去抑制会产生类似于内侧视前区注射 GABA(A)受体激动剂和神经元抑制剂 muscimol 所引起的生理和行为变化。我们通过评估双侧注射 muscimol 到 DMH 对这些变化的影响来检验以下假设，即从中脑导水管周围灰质区诱发的所有这些效应都是通过背内侧下丘脑神经元介导的。在向背内侧下丘脑注射载体后，向内侧视前区注射 muscimol 会引起心率、动脉压、体温、血浆促肾上腺皮质激素和运动活动的显著增加，并且还会增加下丘脑室旁核中的 c-Fos 表达，已知该核控制促肾上腺皮质激素从腺垂体的释放。双侧背内侧下丘脑注射 muscimol 会适度抑制基础心率和体温，但完全消除了从中脑导水管周围灰质区诱发的所有变化。在背内侧下丘脑前侧注射 muscimol 对从中脑导水管周围灰质区诱发的自主神经和神经内分泌变化没有影响。因此，背内侧下丘脑神经元的活动介导了从中脑导水管周围灰质区诱发的一系列生理和行为反应，表明后者区域代表了背内侧下丘脑关键神经元的抑制性调定点。
