Calcium directly permeates kainate/alpha-amino-3-hydroxy-5-methyl-4- isoxazolepropionic acid receptors in cultured cerebellar Purkinje neurons.

In cultures of rat cerebellar neurons that were enriched in Purkinje cells, the non-N-methyl-D-aspartate glutamate receptor agonist kainate (KA) stimulated Ca2+ influx into all neurons in Na(+)-containing solutions. A large Ca2+ influx was also observed in most neurons when KA was applied in Na(+)-free solutions, even when the cells were voltage-clamped at negative potentials. KA also stimulated Co2+ uptake into both Purkinje and non-Purkinje neurons. The KA-induced Ca2+ influx was insensitive to pharmacological antagonists of voltage-sensitive Ca2+ channels and antagonists of N-methyl-D-aspartate receptors. Thus, different types of cerebellar neurons possess KA-gated ionophores that are permeable to Ca2+. This Ca2+ conductance may play an important role in glutamate-mediated physiological and pathological events in the cerebellum.