脑内γ-氨基丁酸(GABA)在急性失血性低血压时对血压的影响

THE EFFECT OF CEREBRAL GABA ON BLOOD PRESSURE DURING ACUTE HEMORRHAGE

本实验通过大鼠和家兔侧脑室注射GABA受体阻断剂荷包牡丹碱(Bicuculline)研究正常血压和急性失血性低血压时,中枢GABA对血压的调节作用。结果表明:在两种情况下,荷包牡丹碱均有明显的升压作用,但后者显著大于前者,且这种升压效应不被去肾或去肾上腺所影响。同时发现:急性失血性低血压时,兔脑脊液中GABA含量明显增加,提示在急性失血性低血压时,中枢GABA具有阻止血压回升的作用,这种作用是通过对中枢交感神经系统的抑制引起的。

Intracerebroventricular (i. c. v.) injection of bicuculline methochloride 2uuuuuuuuuuug and 0.5uuuuuuuuuuuug, an GABA receptor antagonist, resulted in an increase of blood pressure in urethaneanesthetized rats and rabbits. This increase in blood pressure was found to be more potent during the hypotension induced by acute bleeding from carotid artery than that in normal blood pressure and it was not affected by adrenalectomy and nephrectomy. The lower the basal blood pressure, the higher the blood pressure induced by bicuculline. There is a significant negative correlation between the basal blood pressure and the increase in blood pressure induced by bicuculline (Y= 87.9-0.34X, r=-0.49, n = 22, p<0.05, in rats; Y=31.9-0.37X, r=-0.55, n=16, p<0.05, in rabbits), It was also found a significant negative correlation between the basal blood pressure and the increase in the discharge in splanchnic nerve induced by the i. c. v. injection of bicuculline in the rat (Y = 414-3.28X, r=-0.63, n = 14, p<0.05). The GABA content in cereb-rospinal fluid obtained from cisterna cerebellomedullaris cannula in rabbits increased during the bleeding. All this results suggest that under the conditions of low blood pressure induced by acute bleeding the suppressive effect of GABAergic system in central nervous system on blood pressure is more potent than that in normal conditions.