Stereoselective S-nitrosocysteine recognition sites in rat brain

We examined the effects of intracisternal (i.c.) injections (10–250 nmol) of the l- and d-isomers of S-nitrosocysteine ( l- and d- S-nitrosocysteine) on the mean arterial blood pressure and heart rate of conscious 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 pressure and heart rate which were followed by increases in these parameters. The i.c. injection of d- S-nitrosocysteine did not produce initial falls in mean arterial blood pressure or heart rate but produced the subsequent increases in these parameters. l- and d- S-nitrosocysteine decomposed 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.