DEVELOPMENTAL EXPRESSION OF EXCITATORY AMINO-ACID RESPONSES IN CEREBELLAR PURKINJE NEURONS IN CULTURE

We have examined the developmental expression of excitatory amino acid responses in cerebellar Purkinje neurons using a culture model system, extracellular recording techniques and micropressure application of agonists. In mature cultured Purkinje neurons, glutamate (Glu) and the selective receptor agonists quisqualate (Quis) and kainate (KA) elicited multiphasic responses with both excitatory and inhibitory phases. N-methyl-D-aspartate was ineffective. The agonist responses were characterized by an initial excitatory period, a period of burst activity and an inhibitory period. Glu, Quis and KA differed in the ability to evoke the 3 response components. Quis was the most potent agonist and the most effective in producing burst activity and an inhibitory period. Immature Purkinje neurons without visible dendritic structure also exhibit prolonged multiphasic responses when tested with the 3 agonists. However, response components were generally less robust than in mature neurons. Developmental changes in response properties were observed for all agonists, but the developmental changes in total response duration and the duration of the inhibitory period observed for the Quis response were not observed for the Glu or KA responses. These data can be explained by the presence of multiple excitatory amino acid receptor subtypes in both mature and immature Purkinje neurons.