The Mechanism Of Nicotine Involved In Sensory Stimulation-induced Field Potential Response In Mouse Cerebellum

Objective:To investigate the effect of nicotine on the sensory stimulation-induced field potential responses by pharmacological and electrophysiological methods,to explore the mechanism of nicotine modulates the sensory information transmission in the cerebellar cortical molecular layer in vivo in mice.We aimed to reveal the mechanism of nACh receptors involved in sensory information transmission and integration in the molecular layer of cerebellar cortex.Methods:Kunming mice were selected from 40 days to 60 days after birth,weighed and administered to the peritoneal cavity of mice by using urethane at a dose of 1.3 g/kg.The mice were placed on a fixed treatment device,and after sufficient pre-treatment,the cerebellum Crus ? area was drilled under strict protection,about 1-1.5 mm,and the brain tissue must be completely protected from injury.And remove the surface skull.The dura mater was removed with the support of a microscope,and an oxygenated artificial cerebrospinal fluid(ACSF)was continuously perfused with a peristaltic pump on the fully exposed brain surface.Nicotine,hexamethyl ammonium chloride(Hexa),methyl taurine(MLA),dihydro-beta-erythromycin hydrobromide(DbetEH)and other drugs were applied to the cerebellum surface by cerebral surface perfusion.The trigeminal nerve sensory stimulation was performed by air-puff(50-60 ms,50-60 psi)to the ipsilateral beard pad using ae blower device.The electrophysiological results were recorded by computer and the data were collected by data software.Through the integration of sensory stimulation induced molecular field potential changes;Clampfit software(version 11)was used for data analysis,and SPSS21.0 software was used for statistical analysis of data.Paired t test was used before and after drug administration.P<0.05 was considered statistical difference.Results:(1)Under the anesthetic state,the field potential response in the cerebellar molelayer can be evoked by air-puff stimulation,which expressed a rapid negative polar wave followed by a larger positive polar wave.After continuous perfusion of Nicotine(1mM)on the brain surface,the area under the curve(AUC)of inhibitory component of P1 in the molecular layer of cerebellar cortex decreased significantly,accompanied by a significant decrease in the amplitude of P1.(2)Nicotine had no significant effect on the latency of sensory stimulation-induced molecular layer field potential,but the time of P1 production was longer and the delay time was shorter than that before administration.In addition,nicotine can significantly reduce the amplitude of N1 wave and AUC of N1,but there is no difference in the starting time of N1 negative wave before and after nicotine treatment,and the starting time of P1 is significantly earlier.(3)In the presence of non-selective nACh receptor blocker Hexa,the decrease of P1 amplitude and AUC was not observed,nor was the change of N1 amplitude and AUC observed.This suggests that non-selective nACh receptor blocker Hexa completely blocked the effect of nicotine on the sensory stimulation-evoked field potential in cerebellar molecular layer.(4)In the presence of selective ?4?2 subtype nACh receptor blocker,D?EH,application of nicotine still produced a significant decrease in the amplitude of field potential response P1 in the molecular layer of cerebellar cortex,accompanied by a significant decrease in AUC.The results showed that the selective ?4?2 subtype nACh receptor blocker did not block the effect of nicotine on the field potential response in the molecular layer of cerebellar cortex.(5)In the presence of selective a-7 subtype nACh receptor blocker MLA,the amplitude of P1 and AUC did not change significantly after nicotine was perfused on the brain surface.It was suggested that MLA,a selective ?7 subtype nACh receptor blocker,completely blocked the inhibitory effect of nicotine on the field potential response in the molecular layer of cerebellar cortex induced by sensory stimulation in mice.Conclusions:(1)Nicotine inhibits the GABAergic component of the molecular field potential in the cerebellar cortex induced by sensory stimulation,and affects the waveform dynamics,leading to earlier inhibition time,but less amplitude and area under the waveform.(2)The inhibitory effect of nicotine on sensory stimulation-induced field potential response in the cerebellar cortex of mice is achieved by activating the a7 subtype nACh receptor,not the ?4?2 subtype nACh receptor.(3)The results suggest that nicotinic receptors play an important role in the regulation of information transmission in the cerebellar cortex and may participate in the motor learning function of the cerebellum.