The Morphological And Electrophysiological Properties Of CR Positive Interneurons In The Mouse Striatum

Background: The striatum is the main input nucleus of the basal ganglia and the main component of the motor center.It is mainly involved in regulation of voluntary movement,involuntary movement,muscle tension,body posture and fine movement,as well as regulation of motivation,emotion and reward.The striatum mainly receives the excitatory input from the cortex.After processing by MSNs and interneurons,the striatum is transmitted back to motor cortex through thalamus to perform motor functions.There are two types of striatal interneurons: Cholinergic and GABAergic interneurons,among which GABAergic interneurons are classified into PV+ interneurons,NPY+ interneurons and CR~+ interneurons.Previous studies have suggested that cholinergic interneurons are mainly involved in motor decision-making and conversion,PV+ interneurons are involved in feedforward regulation,and NPY+ interneurons release somatostatin to regulate blood vessels and glial cells.However,at present,the morphological characteristics of CR~+ interneurons are only limited to immunohistochemical level,and the morphological and electrophysiological characteristics of CR~+ inteneurons are lack of studies.Obiective: To analyze the morphological and electrophysiological characteristics of CR~+ interneuron and speculate the biological function of CR~+ interneuronMethod: The CR-cre mice were hybridized with Ai32 mice,and the double positive mice were screened through gene identification.The mice which CR + interneurons with e YFP were obtained(CRx Ai32).Firstly,the brain of wild-type mice was infused and sectioned,and the distribution of CR~+ interneurons in the striatum was observed by immunohistochemical technique.Then the brains of CRx Ai32 mice were infused with section fluid,and the brain slices containing the striatum were obtained by vibrating slicer and placed into incubator for 30 minutes.The CR~+ interneurons were patched under the irradiation of blue laser and stained by Biocytin.At the same time,the electrophysiological properties of interneurons were recorded.Finally,different antagonists were added to interneurons to record their m EPSCs and m IPSCs.In the same way,PV-cre mice were hybridized with Ai35 mice to record the electrophysiological characteristics of PV+ interneurons and medium spiny neurons,as well as their m EPSCs and m IPSCs.Results:(1)Morphological characteristics: The somatic shape of CR~+ interneurons were mainly round and oval,with more dendritic branches and smooth surface and no obvious dendritic spines,showing typical morphological characteristics of interneurons.According to the size of the soma: B-CR~+ type had large body and more dendrites,and usually separated 2~3 thicker dendrites from the adjacent body.The M-CR~+ type is medium-sized,with sparse dendrites and few branches.S-CR~+ type has small body,more branches of dendrites,and curved dendrites around the body.(2)Electrophysiological parameters:(1)The membrane capacitance of CR~+ and PV+ interneuron were similar(P > 0.05),but less than that of MSN(P < 0.001).(2)The input resistance of CR~+ interneuron was similar to that of PV+ interneuron and MSN(P > 0.05),and the input resistance of PV+ interneuron was higher than that of MSN(P < 0.05).(3)The holding current of CR~+ interneuron was lower than that of PV+ interneuron(P < 0.05),but the holding current of CR~+ and PV+ interneuron was more than that of MSN(P < 0.001).(4)There was no difference in the absolute value of resting membrane potential between CR~+ interneuron and PV+ interneuron(P > 0.05),but they were lower than that of MSN(P < 0.001).(5)The maximum firing frequencies of CR~+ and PV+ interneuron were similar(P > 0.05),and both were higher than those of MSN(P < 0.001).(6)The action potential half-width of CR~+ and PV+ interneuron was similar(P > 0.05),and lower than that of MSN(P < 0.001).(3)Postsynaptic current:(1)m EPSCs: The m EPSCs amplitude of CR~+ interneuron,PV+ interneuron and MSN was different(P < 0.05),and the amplitude of PV+ interneuron are less than the trend of MSN(P = 0.08).For m EPSCs frequency,the frequency of CR~+ interneuron and the PV+ interneuron was similar(P > 0.05),and were more than that of the MSN(P < 0.001).(2)m IPSCs: There are no difference between CR~+ interneuron,PV+ interneuron and MSN in the m IPSCs amplitude(P > 0.05).For m IPSCs frequency,the frequency of PV+ interneuron was higher than those of CR~+ interneuron(P < 0.001)and MSN(P < 0.001).There was no difference between CR~+ interneuron and MSN(P > 0.05).Conclusion: CR~+ interneuron have typical morphological characteristics and can be divided into three types.Electrophysiological parameters and postsynaptic current characteristics of CR~+ interneuron indicate that they have same biological functions as PV+ interneuron and involved in feedforward inhibition.