Effects Of Norepinephrine On Spontaneous Complex Spikes Of Cerebellar Purkinje Cell In Vivo In Mice

[Objective]It has been reported that application of norepinephrine(NE)to cerebellar cortex or activation of the locus coeruleus(LC)induced a decrease in spontaneous simple spike(SS)firing activity of Purkinje cell(PC).Our previously results indicated that NE bidirectional modulated the spontaneous SS activity of PC via enhancing both inhibitory inputs from molecular layer interneuron(MLI)and excitatory inputs of parallel fibers.However,the effects of NE on the spontaneous complex spikes(CS)activity of cerebellar PC in living mouse have not yet been fully understood.In the present study,we examined the effects of exogenous NE on the CS activity of PC in urethane-anesthetized mice by electrophysiological and pharmacological methods.[Methods]1.Anesthesia and surgical procedures,mice were anesthetized with urethane(1.3 g/kg body weight,intraperitoneal injection).The mice were tracheotomized to avoid respiratory obstruction and fixed on a custom-made stereotaxic frame.After a watertight chamber was created,a 1-1.5 mm craniotomy was drilled to exposethe cerebellar surface corresponding to vermis and Crus ?.The dura mater was carefully removed,the brain surface was constantly superfused with oxygenated artificial cere-brospinal fluid(ACSF).Therectal temperature was monitored,and maintained at 37.0±0.2?.2.Electrophysiological recording,the in vivo cell-attached recordings from PCs were performed with an Axopatch-200B amplifier.PCs were identified by the presence of both SS and CS under cell-attached recording conditions3.Pharmacologic research,the brain surface was constantly superfused with ACSF or drugs and simultaneously recorded activity of PCs.4.Statistical analysis,all data are expressed as the mean ±S.E.M.Differences between the mean values recorded under control and test conditions were evaluated with the Student's paired t-test and ANOVA using SPSS(Chicago,IL)software.P values below 0.05 were considered to indicate a statistically significant difference between experimental groups.[Results]1.NE did not affect frequency of CS.2.NE decreased the number of CS spikelets in PC,but without changing instant frequency of the CS spikelet.3.NE did not affect amplitude of CS,but significantly decreased the area under curve(AUC)of CS.4.NE induced increases in the CS-evoked pause of SS firing.5.Application of a-adrenergic receptor antagonist,phentolamine,blocked the NE-induced inhibition of CS of PC.[Conclusion]NE was not only decrease the SS activity of PCs but also affected the spontaneously CS activity of PCs by a-adrenergic receptor in mice in vivo.These suggested that NE neurons of LC could regulate the ability of clambing fibers from the inferior olive nucleus control the activity of PCs.