Neural factors in experimental degenerative arteriopathy

Intermittent electrical stimulation of the lateral hypothalamus of rats performed for 30 min to 6 hr, results in hyperlipidemia and endothelial cell damage of the aorta and coronary arteries. Hyperlipidemia is related to transient biliary obstruction elicited by hypothalamic stimulation and is characterized by elevation of the cholesterol, phospholipid, and triglyceride fractions. Endothelial cell damage is observed ultrastructurally as plasma membrane degeneration with detachment and the formation of large spaces ("vacuoles"). Thus, neural factors may be implicated in inducing conditions associated with early atherogenesis. Stimulation carried out for longer time intervals would be expected to produce more advanced lesions. However, the role of neural transmission per se (i.e., without hyperlipidemia) in producing arteriopathy is not clearly defined from these experiments. In rats, the lesser splanchnic nerve forms the major innervation of the abdominal aorta. In animals fed normal diets, chronic intermittent stimulation of this nerve (up to 3 weeks) resulted in advanced arteriosclerotic changes with intimal fibrosis and calcification. On histologic examination, lipid deposits appeared to be absent from these lesions. Animals stimulated for shorter periods of time exhibited earlier changes associated with atherogenesis, such as endothelial damage, elastic reduplication, and adherent microthrombi. Thus, direct neural transmission, especially if excessive, plays a role in producing arteriopathy. Hyperlipidemia, if persistent, could modify these lesions so that they would accumulate plasma lipids. Experiments to test this hypothesis are currently in progress.