Potent metabolic stimulation of septal gray and cerebral white matter in vivo by intraventricular endothelin and nitric oxide.

Endothelin-1 (ET) and sodium nitroprusside (SNP, which liberates nitric oxide, NO) were given alone or together into a lateral cerebral ventricle (icv) of anesthetized rats to assess their potential interaction on cerebral rates of glucose metabolism (autoradiographic [14C]deoxyglucose technique). ET (9 pmol) produced hypermetabolic effects ipsilaterally in the septal nuclei and periventricular white matter. NO lesioned the septum, which displayed neuronal damage and diminished metabolic activity, and evoked potent increases in glucose metabolism bilaterally in commissural and projection white matter tracts. Together, ET and NO had synergistic hypermetabolic effects in the hippocampal fimbria, but were antagonistic on the metabolic rate of the lateral septal nucleus and choroid plexus. The results reveal an extraordinary sensitivity in the metabolic rate of septal gray matter to ET and of white matter fibers to NO in vivo. Icv administration offers a useful approach for examination of the metabolic and toxicological properties of the novel neurotransmitter substances ET and NO on septal neurons, myelinated fibers, and choroidal epithelia.