Effect Of Propofol On Cerebellar Cortical PF-PC Synaptic Transmission

[Objective]To examine the effect of propofol on the cerebellar Parallel fiber-Purkinj e cell(PF-PC)synaptic transmission in acute mouse cerebellar slices by whole-cell recording technique and pharmacological methods in absence of γ-aminobutyric acid A receptor(GABAAR)and glycine receptors(GlyR)activity.[Methods]ICR mice 4-7 weeks after birth were selected as experimental animals.After anesthesia with isoflurane inhalation,the head was quickly severed and the brain was extracted.Then,sagittal sections were prepared with a vibrating slicer with a thickness of 300 microns.At 24-25 degrees Celsius,cerebellar sections were incubated for more than 60 minutes in an artificial cerebrospinal fluid(ACSF)mixed with 95%O2 and 5%CO2 for electrophysiological recording under a microscope.The stimulation electrode was placed in the molecular layer to stimulate parallel fibers,with the paired stimulus pulse of 0.5 Hz(0.2 ms;10-100 A stimulus intensity;duration 50 ms),and the excitatory postsynaptic current(EPSC)of purkinne cells was recorded by patch clamp amplifier(Axopatch-700B)and data acquisition software.The experiments described below were conducted with the application of picrotoxin(50 μM)and strychnine(2 μM),which blocked the inhibition currents mediated by GABAAR and GlyR.Clamp fit 10.3 software was used to analyze the electrophysiological experimental data.Mean+/-SEM was used to express the data of each group.One-way ANOVA and Mann-Whitney-Wilcoxon test(SPSS software;Chicago,IL,USA)was used to determine the level of statistical significance between groups of data.P<0.05 was considered to be significantly different.[Results](1)With the blockade of GABAA and glycine receptors activity,propofol reversely decreased the amplitude of PF-PC excitatory postsynaptic currents(PF-PC EPSCs),accompanied with a significant increase in paired-pulse ratio(PPR).(2)The propofol-induced decrease in amplitude of PF-PC EPSCS was reversible and concentration-dependent.And the half-inhibitory concentration(IC50)of propofol for inhibiting PF-PC EPSCs was 4.7 μM.(3)Application of N-methyl-D-aspartic acid receptor(NMDAR)antagonist,D-2-Amino-5-phosphonovaleric acid(D-APV)(50 μM)failed to abolish the effect of propofol on PF-PC synaptic transmission.(4)The propofol-induced changes in amplitude and PPR of PF-PC EPSCs were completely blocked by y-aminobutyric acid B receptor(GABABR)antagonist,saclofen(10 μM).(5)Application of GABABR agonist,baclofen induced a decrease in amplitude and an increase in PPR of PF-PC EPSCs,as well overwhelmed the propofol-induced changes in PF-PC EPSCs.(6)The propofol-induced changes in amplitude and PPR of PF-PC EPSCs were abolished by a specific protein kinase A(PKA)inhibitor,KT5720.[Conclusion](1)Propofol concentrate-dependently inhibits PF-PC synaptic transmission in mouse cerebellar slices,with the blockade of GABAAR and glycine receptor.(2)Propofol facilitates presynaptic GABABR,resulting in an inhibition of PF-PC synaptic transmission via PKA signaling pathway in mouse cerebellar cortex.