Differential regulation of cerebellar granule neurons by two types of quisqualate receptors.

Stimulation of the quisqualate (QA) subtype of glutamate receptor increased the expression of phosphate activated glutaminase (needed for neurotransmitter glutamate synthesis) and the ability to release neurotransmitter glutamate in cultures of glutamatergic cerebellar granule neurons. In contrast, QA had no significant effects on the lactate dehydrogenase activity and amount of protein. The QA-mediated elevation in glutaminase activity was blocked by the ionotropic QA receptor antagonist CNQX and mimicked by the ionotropic QA receptor agonist AMPA, but not by the metatropic QA receptor agonist t-ACPD. The increase in Ca2+ influx essentially through activation of L-type channels, and not the mobilization of internal Ca2+ stores, was responsible for these QA receptor-mediated long-term changes in cerebellar granule neurons.