Nasimi Ali, Hatam Masoumeh
Department of Physiology, Isfahan University of Medical Sciences, Iran.
Exp Brain Res. 2005 Nov;167(2):268-75. doi: 10.1007/s00221-005-0035-9. Epub 2005 Nov 15.
The horizontal limb of diagonal band of Broca (hDB) is a part of the limbic system. It has been shown that microinjection of L-glutamate into the hDB elicited cardiovascular depressive responses in anesthetized rats and pressor effect in unanesthetized rats. But the role of glutamate receptor subtypes has not yet been investigated. In addition the role of the GABAergic system of the hDB in cardiovascular responses is not known. Therefore, we examined the cardiovascular responses elicited by glutamate and GABA receptors in the hDB by using their agonists and antagonists. Drugs (50 nl) were microinjected into the hDB of anaesthetized rats. Blood pressure and heart rate were recorded before and throughout each experiment. The average changes in the mean arterial pressure and heart rate at different intervals were compared both within each case group and between the case and control groups using repeated measures of ANOVA. Microinjection of GABA(A) receptor antagonist, bicuculline methiodide (BMI, 1 mM) increased both the mean arterial pressure and heart rate, and muscimole, a GABA(A) agonist (500 pmol) caused a significant decrease in the mean arterial pressure and heart rate. Microinjection of L-glutamate (0.25 M) into the hDB resulted in a maximum decrease of the mean arterial pressure of 24.4 +/- 3.7 mmHg and heart rate of 25.2 +/- 3.08 beats/min. Injection of AP5, an antagonist of glutamate NMDA receptor (1 and 2.5 mM), and CNQX, an antagonist of glutamate AMPA receptor (0.5 and 1 mM) caused small, nonsignificant changes of the heart rate and the blood pressure. Either AP5 or CNQX when coinjected with glutamate abolished the depressor effect of glutamate, suggesting that simultaneous activation of both glutamate receptors is necessary for the effect of glutamate to emerge. The depressor effect of the glutaminergic system of the hDB on the cardiovascular system was similar to the previous studies. For the first time, the effects of CNQX, AP5, BMI, and muscimole have been shown in this study.
布罗卡斜角带水平支（hDB）是边缘系统的一部分。研究表明，向hDB微量注射L-谷氨酸可在麻醉大鼠中引发心血管抑制反应，而在未麻醉大鼠中引发升压效应。但谷氨酸受体亚型的作用尚未得到研究。此外，hDB的GABA能系统在心血管反应中的作用尚不清楚。因此，我们通过使用谷氨酸和GABA受体的激动剂和拮抗剂来研究hDB中这些受体引发的心血管反应。将药物（50 nl）微量注射到麻醉大鼠的hDB中。在每个实验之前和整个过程中记录血压和心率。使用重复测量方差分析比较每个病例组内以及病例组与对照组之间不同时间间隔的平均动脉压和心率的平均变化。微量注射GABA(A)受体拮抗剂甲磺酸荷包牡丹碱（BMI，1 mM）可使平均动脉压和心率升高，而GABA(A)激动剂蝇蕈醇（500 pmol）可使平均动脉压和心率显著降低。向hDB微量注射L-谷氨酸（0.25 M）导致平均动脉压最大降低24.4±3.7 mmHg，心率最大降低25.2±3.08次/分钟。注射谷氨酸NMDA受体拮抗剂AP5（1和2.5 mM）以及谷氨酸AMPA受体拮抗剂CNQX（0.5和1 mM）会使心率和血压发生微小的、不显著的变化。当AP5或CNQX与谷氨酸共同注射时，可消除谷氨酸的降压作用，这表明谷氨酸受体的同时激活对于谷氨酸发挥作用是必要的。hDB的谷氨能系统对心血管系统的降压作用与先前的研究相似。本研究首次展示了CNQX、AP5、BMI和蝇蕈醇的作用。
