IONOTROPIC GLUTAMATE RECEPTORS AND NITRIC-OXIDE SYNTHESIS IN THE RAT STRIATUM

A population of interneurones in the rat striatum contain neuronal nit ric oxide synthase (nNOS). The nitric oxide (NO)-cGMP pathway may modu late neurotransmission in this brain area but little is known about th e physiological stimulator(s) of nNOS in striatal neurones. Exposure o f intact striatal slices to N-methyl-D-aspartate (NMDA) (100 mu M, 8 m in) caused an almost two-fold increase in cGMP levels (EC50 similar to 25 mu M), which was inhibited by the nNOS inhibitor N-omega-L-nitroar ginine (IC50 similar to 70 nM) and by removing external Ca2+. Neither (S)-alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate (AMPA) nor t he kainate receptor agonist (2S,4R)-4-methylglutamate increased basal cGMP levels. Thus, glutamatergic striatal inputs could stimulate a NO- cGMP pathway in the striatum via NMDA receptors but not via AMPA or ka inate receptors.