STEREOSELECTIVE S-NITROSOCYSTEINE RECOGNITION SITES IN RAT-BRAIN

We examined the effects of intracisternal (i.c.) injections (10-250 nm ol) of the L- and D-isomers of S-nitrosocysteine (L- and D-S-nitrosocy steine) on the mean arterial blood pressure and heart rate of consciou s rats, and the decomposition of L- and D-S-nitrosocysteine to nitric oxide (NO) upon addition to brain homogenates. The i.c. injection of L -S-nitrosocysteine produced initial falls in mean arterial blood press ure and heart rate which were followed by increases in these parameter s, The i.c. injection of D-S-nitrosocysteine did not produce initial f alls in mean arterial blood pressure or heart rate but produced the su bsequent increases in these parameters. L- and D-S-nitrosocysteine dec omposed equally to NO. These results suggest that the initial effects of L-S-nitrosocysteine may be due to the activation of stereoselective recognition sites on brain neurons.