Neuronal nitric oxide has a role as a perfusion regulator and a synaptic modulator in cerebellum but not in neocortex during somatosensory stimulation - An animal PET study

To clarify a role of neuronal nitric oxide in neurovascular coupling, we performed cerebral blood flow (CBF) and cerebral metabolic rate of glucose (CMRglc) measurements with positron emission tomography in somatosensory-stimulated cats using a specific neuronal nitric oxide synthase inhibitor, 7-nitroindazole (7-NI). The effect on flow-metabolism coupling were tested by global and regional-specific changes on CBF and CMRglc, and the regional-specific effect was estimated both by regions of interest (ROI) and voxel-based (VB) analysis using globally-normalized CBF and CMRglc changes. The electrical somatosensory stimulation in the unilateral forepaw elicited coupled increase in CBF and CMRglc in the contralateral somatosensory cortex (7%) and the ipsilateral cerebellum (8%). 7-NI induced 20% decrease in global CBF both during rest and activation, but not in global CMRglc at simulation. Both ROI and VB analysis showed that 7-NI induced an increase in CMRglc (13%) in the ipsilateral cerebellum compared to control under vehicle alone, but it was accompanied by only 8% increase in CBF, suggesting uncoupling of flow-metabolism while it induced any perturbations in the contralateral somatosensory cortex. These observations suggest that neuronal nitric oxide has an important role for a mediator of regional neurovascular coupling as well as synaptic modulator in the cerebellum, but less so in the neocortex. (C) 2002 Elsevier Science Ireland Ltd and the Japan Neuroscience Society. All rights reserved.