Effect of midazolam onsynaptic transmission in rat hippocampal CA1 area

Abstract

：Objective To investigatethe effect of midazolam on synaptic transmission in stratum radiatum of CA1 area of rathippocampus and the underlying mechanism. Methods Thirty-five adult male Wistar ratsweighing 190-220 g were randomly divided into 7 groups ( n = 5 each) . Two types ofstimulation were used: single stimulation and paired pulse stimulation. Four groups undersingle stimulation: control group (group C_1), bicuculline group (group B_1 ), midazolamgroup (group M_1) and bicuculline + midazolam group (group BM). Three groups under pairedpulse stimulation: control group ( group C_2 ), bicuculline group (group B_2 ) andmidazolam group (group M_2 ) . The animals were anesthetized with intraperitoneal (IP)pentobarbital 50 mg/kg. The stimulating and recording electrodes were inserted into thestratum radiatum of CA1 area of the hippocampus. The interval between the 2 pulsestimulation was 30 ms. Excitatory post-synaptic potential (EPSP) was elicited before(baseline) and after IP bicuculline (2 mg/kg) or/and midazolam (3 mg/kg) administration.The EPSP amplitude was recorded during single stimulation. EPSP_2 /EPSP_1 ( E_2 /E_1 )ratio was recorded during paired pulse stimulation. Results Compared with group C, , theEPSP amplitude was significantly decreased in group M, ( P 0.05) . Compared with group C_2 ,E_2 and E_2/E_1, ratio were significantly increased in group B_2 , while E_1 , E_ 2, andE_2/E_1, ratio were significantly decreased in group M2 ( P < 0.05). E_1, E_2 and E_2/E_1, ratio were significantly lower in group M_2 than in group B_2 (P < 0.05) .Conclusion Midazolam can reversibly depress the excitatory synaptic transmission efficacyin the CA1 area of the rat hippocampus through presynaptic inhibitory circuit. CABA_Areceptor is not directly disturbed.