MK-801 blocked the functional NMDA receptors in identified cerebellar neurons

In order to clarify the nature of N-methyl-D-aspartate (NMDA) receptors in cerebellum, where heterogeneity of the NMDA receptor has been suggested, we investigated the action of MK-801 on the NMDA-induced [Ca²⁺]_i rise in cultured cerebellar neurons using video-assisted microfluorometry. MK-801 caused a potent and selective blockade of the NMDA-activated [Ca²⁺]_i elevation. The blockade caused by MK-801 was dependent on the presence of NMDA, i.e., use-dependent. There was no difference in the mode of blockade between immunocytochemically identified Purkinje and non-Purkinje cells, although the relative size of the NMDA-induced [Ca²⁺]_i rise was significantly less in Purkinje cells. These results indicate that the NMDA receptors in cultured cerebellar neurons are coupled with the same channels as those in other brain regions.