The Study On Mechanism Of Motor Dysfunction Caused By The Loss Of CDK5 In Cholinergic Neuron

OBJECTIVE:CDK5 is widely expressed in the central nervous system and plays an important role in neural development,post-mitotic neuronal survival and synaptic plasticity.Studies of CDK5 were mainly focused on pyramidal neurons,and CDK5 involved in different brain regions or different types of neurons regulate various behavioral representations.Central cholinergic nervous system also plays a significant role in body function,and the functional regulation of CDK5 in cholinergic neurons remains to be studied.In this study,Cre/loxp system was used to construct the cholinergic neuron-specific Cdk5 knockout mice to study the function of CDK5 in cholinergic neurons.METHODS:1)ChAT Cre mice were mated with Cdk5 ^f/fmice to obtain mice with specific Cdk5gene knockout in cholinergic neurons(ChAT Cre;Cdk5 ^f/f).2)the behavioral phenotype changes of mice were observed through behavioral experiments.3)the changes of proteins‘expression in striatum were checked by western blotting.4)in vitro patch clamp technique was used to detect changes in the activity of cholinergic interneurons in the striatum.RESULTS:Behavioral tests were performed on mice with specific Cdk5 gene knockout in cholinergic neurons.The total distance of mice in the open-field test did not change significantly.While,in the rotarod test and the traction test,the latency to fall of mice decreased which suggests motor dysfunction of ChAT Cre;Cdk5 ^f/f mice.The results of Y maze test showed that Cdk5knockout on cholinergic neurons did not affect spatial memory.Compared with the control mice,ChAT Cre;Cdk5 ^f/f mice’Choline acetyltransferase expression level was down-regulated significantly,and the expression level of tyrosine hydroxylase increased.In vitro electrophysiological results showed that the resting membrane potential（RMP）,membrane input impedance（Rin）,time constant（Tau）,frequency of action potential and half-peak width of cholinergic intermediate neurons in the striatum were changed.In order to determine the current components that affect the action potential properties,the different types of ion channel currents were further conducted.we found that the BK channel current increased while the recorded sodium current and the transient outward potassium current remained unchanged,which may account for altered activities of cholinergic interneurons.CONCLUSION:The loss of CDK5 in cholinergic neuron results in motor dysfunction and abnormal function of cholinergic system and dopaminergic system in striatum.These phenotypes may be due to the increased excitability of cholinergic interneurons in the striatum which may be induced by increased BK channel currents following the absence of CDK5.