Activation of nitric oxide pathway mediated by metabotropic glutamate receptors in primary cultures of cerebellar granule cells

Abstract

Stimulation of L-glutamate receptors (GluRs) is thought to produce neuron death through the elevation of free intracellular Ca²⁺ levels, leading to activation of Ca²⁺/calmodulin-dependent synthesis of cytotoxic amounts of NO·. In the present study, NO synthase activation mediated by mGluR stimulation is investigated in primary cultures of granule cells (CGrC). It is found that a selective agonist of mGluRs, DL-1-aminocyclopentane-trans-1,3-dicarboxylic acid (ACPD), raises both the cGMP and nitrite (NO₂ ⁻) levels, which are used as a biochemical index to study the enzymatic NO· release from L-arginine. This effect is abolished by applying both Nω-nitro-L-arginine methyl ester (NAME) and DL-2-amino-4-phosphonobytyric acid (AP4), and is independent of Ca²⁺. In contrast, the α-amino-3-hydroxy-5-methylisoxarole-4-propionnate (AMPA)-induced increase in cGMP content is eliminated by the preincubation of CGrC with 4 mM EGTA-chelated Ca²⁺.