ACTIONS OF A METABOTROPIC GLUTAMATE RECEPTOR AGONIST IN IMMATURE AND ADULT-RAT CEREBELLUM

The electrophysiological actions of the metabotropic glutamate receptor agonist IS,3R-1-aminocyclopentane-1,3-dicarboxylic acid (ACPD) on Purkinje and granule cells were studied in immature and adult cerebellar slices. ACPD elicited a depolarizing response when applied to Purkinje cells (EC50) almost-equal-to 20-mu-M). Granule cells hyperpolarised when exposed to low (3-10-mu-M) concentrations of ACPD; higher concentrations produced a depolarisation (EC50 almost-equal-to 40-mu-M) that was rapidly curtailed by a hyperpolarisation. The hyperpolarisation was abolished when Ca2+ was removed. In Purkinje cells, the amplitude of the depolarisation was greater in adult slices compared to those in immature slices. The responses were not blocked by ionotropic glutamate receptor antagonists or (L)-2-amino-3-phosphonopropionate (AP3).