Wible J H, Luft F C, DiMicco J A
Department of Medicine, Indiana University School of Medicine, Indianapolis 46223.
Am J Physiol. 1988 Apr;254(4 Pt 2):R680-7. doi: 10.1152/ajpregu.1988.254.4.R680.
We studied the cardiovascular effects of altering GABA-ergic tone in the posterior hypothalamus in rats. Animals were equipped with chronic guide cannulas placed in the posterior hypothalamus, arterial and venous catheters, and a bipolar electrode on the splanchnic nerve. Microinjected bilaterally into the posterior hypothalamus in conscious rats, the postsynaptic gamma-aminobutyric acid (GABA) antagonists bicuculline methiodide and picrotoxin rapidly increased heart rate, blood pressure, and sympathetic nerve activity. Microinjection of the GABA agonist muscimol into this same region decreased heart rate, blood pressure, and sympathetic nerve activity in conscious rats. In contrast, muscimol infused into the posterior hypothalamus of anesthetized rats failed to alter heart rate or blood pressure. We conclude that 1) the posterior hypothalamus contains a sympathoexcitatory system that is modulated by changes in GABA-ergic tone and 2) tonic GABA-ergic inhibition is sufficient to completely suppress the activity of this hypothalamic sympathoexcitatory system in anesthetized animals but not in conscious rats.
我们研究了改变大鼠下丘脑后部γ-氨基丁酸（GABA）能张力对心血管系统的影响。给动物植入置于下丘脑后部的慢性引导套管、动脉和静脉导管以及内脏神经上的双极电极。在清醒大鼠中，将突触后GABA拮抗剂荷包牡丹碱甲碘化物和印防己毒素双侧微量注射到下丘脑后部，可迅速提高心率、血压和交感神经活动。将GABA激动剂蝇蕈醇微量注射到同一区域，可降低清醒大鼠的心率、血压和交感神经活动。相比之下，将蝇蕈醇注入麻醉大鼠的下丘脑后部，未能改变心率或血压。我们得出结论：1）下丘脑后部存在一个交感兴奋系统，该系统受GABA能张力变化的调节；2）在麻醉动物中，持续性GABA能抑制足以完全抑制该下丘脑交感兴奋系统的活动，但在清醒大鼠中则不然。
