Activation Of GABAergic Neurons In Mouse Brain During Anesthesia Induced By Propofol

General anesthesia has developed 160 years, but the mechanism underlying is still unknown, especially in central nervous system. The researches on mechanism of general anesthesia have always been the unode and focus.Poropfol has been used in induction and maintenance because of its pharmacological merits recent years. But the effect of poropfol on central nervous system is unknown. In vivo and ex vivo researches indicated that poropfol can enhance the binding of GABA and GABAA receptor. There are few research about the presynaptic mechanism. Whether poropfol has effect on presynaptic neurons is the focal point of this study.Objective: Emerging researches have focused on the participation ofγ-aminobutyric acid (GABA) neurons but there still lacks morphological evidence. To investigate the activation of GABAergic neurons during loss of consciousness induced by propofol in the GAD67-GFP knock-in mouse. Methods: 20 GAD67-GFP transgenic mice were used in the present study. The mice were grouped into two, control group and experimental group. Experimental group were grouped into three subsets, T1(5 min), T2(30 min), T3(1 h). Mice in experimental group were injected propofol i.p. 130 mg/kg, and saline was set as the negative control. Mice were graded by ethology while sacrificed at 5 min, 30 min and 1 h after injection, respectively. The whole brain was obtained and cut with a freezing microtome consecutively. Immunohistochemistry and double immuno-fluorescence were performed to observe the Fos expression and the coexistence of Fos and GABA in the whole brain.Results: 1 The scores of ethology were 13 at 5min, 14 at 30 min and 9 at 1h. It indicated that the mice were in the situation of moderate or deep anesthesia at 5 min and 30min, and various transition states at 1h. Expression of Fos protein increased remarkably in CA1, amygdaloid nucleus, thalamic paraventricular nucleus, hypothalamic paraventricular nucleus, hypothalamic ventromedialis nucleus, and periaqueductal gray compared with the control group at three time spots(p<0.05). 2 Neurons expressing Fos protein and GABA simultaneously could be observed in hypothalamic ventromedialis nucleus at 5 min, 30 min and 1 h, the proportion of which among Fos-positive neurons was 80.3%, 89.7% and 91.6%. The double staining neurons could also be seen in PaV, the proportion of which among Fos-positive neurons was T1:19.6%,T2:39.7%,T3:41.6%, C:8.6%。Conclusion: The activation of GABAergic neurons may be one of the mecha- nisms during loss of consciousness induced by propofol.