HETEROGENEITY OF FUNCTIONAL SYNAPTIC PARAMETERS AMONG SINGLE RELEASE SITES

Following alpha-latrotoxin application to cerebellar slices, bursts of miniature IPSCs (mIPSCs) were observed in interneurons of the molecul ar layer. Within bursts, mIPSCs had homogeneous amplitudes with a narr ow Gaussian distribution. Analysis of successive event amplitudes reve aled an interaction between consecutive IPSCs, indicating that bursts originate at single release sites. A mean receptor occupancy of 76% wa s calculated. IPSCs within a burst were analyzed using nonstationary n oise analysis. The results indicate that individual release sites diff er in the number, unitary conductance, and peak opening probability of their postsynaptic channels. In addition, the IPSC decay kinetics wer e very different among release sites. Finally, a significant correlati on was found between several pairs of single site synaptic parameters.