Developmental plasticity in sympathetic nervous system response to fasting in adipose tissues of male rats

While fasting suppresses sympathetic nervous system (SNS) activity in most peripheral tissues, the response of sympathetic nerves in white adipose tissue (WAT) is reportedly stimulatory. To confirm this finding and to determine if the fasting response in WAT is susceptible to developmental modification, SNS activity was compared in fed and fasted animals using techniques of [³H]norepinephrine ([³H]NE) turnover. Studies were performed in commercially reared 7-week-old male rats, in male rats reared in the local vivarium, and in male rats reared until 30 days of age at either 18°C or 30°C. In commercially reared animals, [³H]NE turnover was elevated in epididymal fat during the second day of fasting, a response not seen during the preceding or succeeding day of fasting. On the other hand, in rats reared from birth in the local vivarium a 1-day fast led to suppression of SNS activity in epididymal fat. In rats reared at 18°C for the first 30 days of life, fasting suppressed SNS activity in retroperitoneal fat in contrast to the absence of this response noted in 30°C-reared rats. These studies demonstrate that sympathetic responses in WAT to fasting in young adult, male rats are susceptible to modification by the environmental conditions present during the first month of life.