Sigma-receptor regulation of [3H]arachidonic acid release from rat neonatal cerebellar granule cells in culture.

Sigma receptors have been identified in many brain areas and are especially abundant in those regions known to be involved in control of movement. Sigma receptors have been located autoradiographically in the granule cell layer of cerebellum in adult rat brain. In the current study, we identified sigma receptors in rat neonatal granule cells in culture using radioligand binding. The tritium labeled form of the putative sigma antagonist haloperidol bound with high affinity to membranes prepared from these cells, and ligands selective for sigma receptors competed well against [3H]haloperidol binding. The excitatory amino acid N-methyl-D-aspartate and the direct phospholipase A2 activator melittin stimulated the release of [3H]arachidonic acid from cerebellar granule cells. The N-methyl-D-aspartate-stimulated, but not the melittin-stimulated, release was inhibited in a concentration-dependent manner by the sigma-selective agonist (+)-pentazocine. In addition, the novel sigma 1 agonist BD737 inhibited N-methyl-D-aspartate-stimulated release. Pentazocine inhibition was almost completely reversed by the sigma antagonists NPC-16377 and opipramol. A 1 microM concentration of the phencyclidine receptor-selective ligand MK-801 inhibited approximately 65% of N-methyl-D-aspartate-stimulated release. These results suggest that sigma receptors may play a role in modulating arachidonic acid release in cerebellar granule cells.