Glutamate and aspartate activated channels and inhibitory synaptic currents in large cerebellar neurons grown in culture

Patch-clamp methods were used to examine large (greater than 30 microns) cerebellar neurons of the rat, maintained in cell culture. Cells possessed voltage-activated transient inward Na+ currents which were sensitive to tetrodotoxin. Spontaneous synaptic currents, present in whole-cell recordings, were abolished by bicuculline and picrotoxin and were carried by Cl-. Cells produced inward currents in response to the transmitter candidates glutamate and aspartate and also to the glutamate agonists kainate, quisqualate, N-methyl-D-aspartate and ibotenate. Analysis of glutamate and aspartate-current noise has been used to derive characteristics of the excitatory channels. Single channel currents have also been observed directly in whole-cell and outside-out patches. Both glutamate and aspartate are able to activate channels which were blocked by Mg2+ and had a maximum conductance of 50 pS.