Caloric intake and sympathetic nervous system activity. Implications for blood pressure regulation and thermogenesis

A major problem in elucidating the role played by the sympathetic nervous system (SNS) in the regulation of physiological processes has been the difficulty inherent in the assessment of sympathetic activity. In our laboratory, over the last 8 years, we have utilized techniques to measure the turnover rate of norepinephrine (NE) (the adrenergic neurotransmitter) in sympathetically innervated tissues of laboratory rodents. Because the rate of neurotransmitter turnover is proportional to sympathetic neuronal activity, the application of turnover techniques has permitted us to study the effects of nutrient ingestion on sympathetic activity in the experimental animal. These studies have demonstrated that dietary intake exerts a profound influence on SNS function. Evidence from a variety of sources, recently reviewed, is consistent with the hypothesis that diet-induced changes in SNS activity contribute importantly to dietary changes in thermogenesis. The available evidence also suggests that changes in SNS activity, induced by changes in dietary intake, affect blood pressure; the SNS may therefore play an important role in the relationship between nutrient ingestion and hypertension. The relevant studies conducted in our laboratory over the last 8 years are reviewed herein.