Studies were performed to assess the effect of age on basal sympathetic nervous system activity and on diet-induced changes in sympathetic activity. The rate of norepinephrine turnover in various tissues was measured as an index of sympathetic nervous system activity. In ad lib fed male Fischer 344 rats aged 3 to 24 months, there were no age-related differences in norepinephrine turnover in heart, liver, kidney or pancreas. Throughout the same age range, norepinephrine turnover was greater in organs of sucrose fed than in organs of fasted animals. Diet-induced changes in sympathetic activity thus persist throughout the age range studied.
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