ENDOTHELIAL NITRIC-OXIDE SYNTHASE LOCALIZED TO HIPPOCAMPAL PYRAMIDAL CELLS - IMPLICATIONS FOR SYNAPTIC PLASTICITY

Using antibodies that react selectively with peptide sequences unique to endothelial nitric oxide synthase (eNOS), we demonstrate localizati ons to neuronal populations in the brain. In some brain regions, such as the cerebellum and olfactory bulb, eNOS and neuronal NOS (nNOS) occ ur in the same cell populations, though in differing proportions. In t he hippocampus, localizations of the two enzymes are strikingly differ ent, with eNOS more concentrated in hippocampal pyramidal cells than i n any other brain area, whereas nNOS is restricted to occasional inter neurons. In many brain regions NADPH diaphorase staining reflects NOS catalytic activity. Hippocampal pyramidal cells do not stain for diaph orase with conventional paraformaldehyde fixation but stain robustly w ith glutaraldehyde fixatives, presumably reflecting eNOS catalytic act ivity. eNOS in hippocampal pyramidal cells may generate the NO that ha s been postulated as a retrograde messenger of long-term potentiation.