The role of post-ganglionic parasympathetic nerve fibers from the sphenopalatine ganglion and nasociliary nerve fibers from the trigeminal ganglion in the regulation of basal cerebral blood flow (CBF) was examined using rats, which had been divided into three groups; a sham group, a denervation group and a denervation + NG-monomethyl-l-arginine (l-NMMA) group. In the denervation and denervation + l-NMMA groups, unilateral chronic transection of the above nerve fibers had been performed at the ethmoidal foramen (EF) for 2 weeks. In the sham group, the above nerve fibers were only exposed at EF and not severed 2 weeks before the CBF measurement. Local CBF was measured by the [14C]iodoantipyrine autoradiographic method after intravenous administration of saline in the sham and denervation groups or l-NMMA (30 mg/kg) in the denervation + l-NMMA group. No significant difference in CBF was noted on each side in any of the regions between the sham and denervation groups. l-NMMA induced a significant reduction in local CBF on either side in each brain region. Neither the animals which were administered saline nor those with l-NMMA showed any side-to-side differences in local CBF in any of the brain regions examined. These findings suggest that the perivascular nerve fibers running through the EF, which are known to contain substantial nitric oxide synthase (NOS), may not play a pivotal role in the regulation of basal CBF. The reduction in CBF induced by the acute administration of l-NMMA was not affected by the chronic denervation of the above NOS-containing perivascular nerves.
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