Pyramidal neurones in human precentral gyrus contain nitric oxide synthase

Pyramidal cells in the mammalian neocortex do not normally contain detectable levels of the enzyme nitric oxide synthase. However one region of the human neocortex contains pyramidal neurones that express neuronal nitric oxide synthase activity. These neurons are mainly located in layer V of the precentral gyrus and frontal cortex and are predominantly Betz cells. The proportion of Betz cells stained in the eight brains examined varied from 5 to 80%. The brains of eight rats that had received a stab wound to the parietal cortex were also examined. Following a survival period of 7 or 14 days, small groups of pyramidal neurones surrounding the lesion contained moderate levels of neuronal nitric oxide synthase. We suggest that human pyramidal neurones may start expressing nitric oxide synthase as a response to damage or age-related stress and that the nitric oxide released may have a neuroprotective role.