The Effect Of Sevoflurane Inhalation On The Activations Of GABAergic Neurons And GABA_A Receptor: Observation On The GAD67-GFP Knock-in Mouse

Objective: The mechanisms underlying volatile anesthesia agents are not well elucidated. Emerging researches have focused on the participation ofγ-aminobutyric acid (GABA) neurons but there still lacks morphological evidence. To elucidate the possible activation of GABAergic neurons by sevoflurane inhalation, Fos and green fluorescent protein (GFP) double labeling were used on the brain of glutamic acid decarboxylase (GAD) 67-GFP knock-in mice after sevoflurane inhalation. Methods: Twenty GAD67-GFP knock-in mice were divided into 3 groups: S1 group: incomplete anesthesia state induced by sevoflurane; S2 group: complete anesthesia induced by sevoflurane; control(C) group. Results 1. Real-time PCR and immunohistochemistry results indicated that sevoflurane induced a significant increase of c-fos mRNA in thalamus and hippocampus and protein expression in the dorsomedial hypothalamic nucleus (DM), periaqueductal grey (PAG), hippocampus (CA1, DG), paraventricular thalamic nucleus (PV), lateral septal nucleus (LS), cingulate cortex (Cg1, Cg2) in S1 and S2 group compared with the control group. These alterations on Fos expression were dose-dependent. In S2 group, Fos was only expressed in the amygdale, Edinger-Westphal (E-W) nucleus, arcuate hypothalamic nucleus (Arc) and the ventral part of paraventricular hypothalamic nucleus (PaV). 2. Double immunofluroscent staining indicated that in LS,almost all Fos were present in GABAergic neurons. In CA1, DG, DM, cg1, cg2 and PAG, Fos was expressed as well, but only few were present in GABAergic neurons. Fos expression was very high in paraventricular thalamic nucleus, but no coexistence were found as no GABAergic neuron was detected in this area. 3.The real-time PCR results indicated that in brain stem and thalamus the GABAA receptorα4 subtype mRNA expression upregulated significantly in S1 and S2 groups compared with C group. 4. Double immunofluroscent staining indicated that in brain stem and thalamus Fos were present in neurons that GABAA receptors were expressed in S1 and S2 groups. Conclusion: Our results provided morphological evidence that GABA neurons and GABAA receptors in speific brain areas may participate in the sevoflurane-induced anesthesia.