CHOLECYSTOKININ-INDUCED PROTECTION OF CULTURED CORTICAL-NEURONS AGAINST GLUTAMATE NEUROTOXICITY

The effects of cholecystokinin (CCK) on glutamate-induced neurotoxicity were examined using cultured rat cortical neurons. Brief exposure of glutamate followed by an incubation with normal solution for more than 60 min reduced cell viability by 60-70%, compared with control values. Glutamate-induced neurotoxicity was significantly inhibited by MK-801 and ketamine, which are non-competitive blockers of N-methyl-D-aspartate (NMDA) receptors. Octapeptide CCK-8S and CCK-related decapeptide ceruletide at concentrations of 10(-9)-10(-7) M dose-dependently reduced glutamate-induced neurotoxicity. A desulfated analog CCK-8NS, which acts selectively as an antagonist of CCK(B) receptors, also reduced glutamate neurotoxicity. The neuroprotective effects of CCK were antagonized by L-365260, a CCK(B) receptor antagonist, but not by L-364718, a CCK(A) receptor antagonist. These results suggest that CCK protects cortical neurons against NMDA receptor-mediated glutamate neurotoxicity via CCK(B) receptors.