Effect of hypothalamic stimulation on the endothelial morphology of the aorta in the conscious squirrel monkey

The role of neurogenic factors in the development of atherosclerosis has not previously been studied in detail. In recent years evidence has accumulated to implicate endothelial injury as a primary stimulus for the proliferation of myo-intimal cells resulting in the formation of the early morphologic lesion. In the present investigation, the effect on aortic endothelial morphology of repetitive electrical stimulation of the lateral hypothalamus in the conscious, unrestrained squirrel monkey, maintained on a cholesterol-free low-fat diet, has been studied. Stimulation was performed with a self-powered, miniaturized electronic stimulator connected to indwelling electrodes. Implanted nonstimulated animals served as controls. Endothelial injury in the form of cell degeneration, denudation, with plasma insudation and partial junctional separation were observed electron-microscopically in stimulated animals compared with controls. These alterations were found to be independent of hypercholesterolemia and/or hypertension. Possible pathways for the induction of injury in this neurogenic model are: (1) direct, through neural circuits from the brain to the vessel wall, and (2) indirect, by elaboration of angiopathic substances inside or outside of the CNS, released into the circulation and transported to the vessel wall where they exert their effects. Reversibility of the endothelial injury progression to established lesions and mechanisms involved remain to be determined in further investigations.