Effect of long-term alcohol intake on field potential of cerebellar granule layer in mice and its mechanism / 中华行为医学与脑科学杂志

ABSTRACT

Objective:To investigate the effect of long-term alcohol intake on sensory information synaptic transmission of mossy fiber-granular cells in the cerebellar cortex of mice.Methods:Twenty healthy male ICR mice aged 6 to 8 weeks were divided into normal saline group(control group) and alcohol intake group(alcohol group) according to random number table, with 10 mice in each group. The mice in alcohol group were injected intraperitoneally with 20% alcohol and the mice in control group were injected with the same amount of saline for 28 days.After the injection, the scalp, muscle tissue and skull were removed in turn, and the dura mater was removed to fully expose the crus II area of cerebellum. The mice were stimulated by air blowing at 30 mm of the ipsilateral tentacle pad with a gas jet device.When the the maximal response site was determined, the NMDA receptor antagonist (D-APV), metabolic glutamate receptor 1 antagonist (JNJ16259685) and N-methyl-D-aspartic acid (NMDA) were perfused on the brain surface of mice. Each drug was perfused for 20 minutes and ACSF was used between the two drugs until the waveform was recovered. Patch clamp amplifier was used to record the changes of potential waveform in mouse cerebellar granule layer. The data were analyzed by the softwares of Clampfit 10.3 and SPSS 22.0.Results:After exposure to wind stimulation, the latency of field potential response in granular layer of mice in alcohol group (11.8±0.7)ms was significantly longer than that in the control group (10.1±0.2)ms ( t=-8.041, P<0.05), and the amplitude of N1 (1.2±0.1) MV was significantly lower than that in the control group (0.6±0.1) MV ( t=-12.728, P<0.05). Compared with the control group, the rise time of P1 waveform((4.4±0.2)ms, (3.2±0.2)ms), duration ((12.1±0.5)ms, (10.3±0.2)ms), extinction time((7.8±0.2)ms, (6.9± 0.2)ms), volume under waveform ((7.3±0.2)ms, (4.3±0.2)ms) were significantly increased in the alcohol group ( t=16.100, - 11.840, -11.673, -35.576, all P<0.05). There were no significant differences in the amplitude, half width, rise time and decay time of Roff wave between the two groups ( t=-1.909, -0.910, -0.789, 1.462, all P>0.05). When JNJ16259685 was perfused on the brain surface of mice in alcohol group, the amplitude of field potential evoked by five blowing stimuli had no significant difference compared with that before administration (all P>0.05). When D-APV was perfused into the brain surface of mice in the alcohol group, the amplitude of P1 ((42.3±1.5) Mv)was significantly lower than that before administration ((101.1±0.9)mV) and after elution ((100.1±2.2) mV) ( t=106.762, - 69.605, both P<0.05), and the area under waveform of P1 ((42.6±1.3)%) was also significantly lower than that before administration ((100.6±1.6)%) and after elution ((97.6±2.2)%) ( t=88.862, -67.791, both P<0.05).The ratio of N2 / N1 (0.3±0.1) was significantly lower than that before administration (0.4±0.1) and after elution (0.3±0.1) ( t=2.242, 2.121, both P<0.05). When NMDA was perfused on the brain surface of mice in the control group, compared with before administration and after elution, the amplitude of P1 ((110.7±3.2) mV, (100.1±0.9) mV, (102.0±1.7) mV, t=-10.173, 7.669, both P<0.05), the area under the waveform of P1 ((127.9±3.5)%, (100.0±3.1)%, (115.0±5.3)%, t=-18.698, 6.447, both P<0.05), the ratio of N2 / N1 ((0.5±0.1), (0.3±0.1), (0.3±0.1), t=-5.669, 5.669, both P<0.05) were all significantly increased. When D-APV was perfused on the brain surface of mice in control group, the field potential evoked by blowing stimuli had no significant difference compared with that before administration and after elution (all P>0.05). Conclusion:Long-term alcohol intake significantly suppresses the synaptic transmission of excitatory glutamate in MF-GC, and enhances the inhibitory response mediated by GABAA receptor in cerebellar cortex. The inhibitory component is enhanced by NMDA receptor, but not by type 1 metabolic glutamate receptor.