SYNAPTIC AND NONSYNAPTIC IMMUNOLOCALIZATION OF GABA AND GLUTAMATE ACID DECARBOXYLASE (GAD) IN CEREBELLAR CORTEX OF RAT

The existence of a large number of GABA receptors in the cerebellar mo lecular layer, and the observation of numerous punctate immunoreactive deposits of GABA synthesizing enzyme (GAD) throughout this layer, cou ld indicate the existence of numerous axon terminals that may be invol ved in neurotransmission modulated by GABA. These axon terminals may b e different from those considered classically as cerebellar GABAergic axon terminals. Therefore, we have reinvestigated the localization of GABA- and GAD-immunoreactivites in the cerebellar cortex of the rat wi th the PAP method, using different antisera obtained from rabbits immu nized with GABA, baclofen and GAD. The results observed in our investi gation have demonstrated GABA- and GAD-immunoreactivities in the axon terminals considered classically as GABAergic, as well as in others wh ich, until now, have not been considered GABAergic. This fact leads us to think that the distribution of GABA or molecules structurally simi lar to GABA is far more extended than previously thought in the cerebe llum. We have also observed both GABA- and GAD-immunoreactivities with in dendrites and glial cells. These facts suggest us a possible extras ynaptic release of GABA.