Isoproterenol alters nonshivering thermogenesis in the Zucker obese rat (fafa)

To test nonshivering thermogenic (NST) capacity of lean and obese Zucker rats, 4 doses of isoproterenol, ranging in concentration from 0.25 to 6.0 micrograms/min . kg . 75, were intravenously infused into 16 to 18 week old male rats, and oxygen consumption was continuously monitored. Obese rats had a decreased NST response relative to lean littermates. This lowered thermogenic response of the obese rats cannot be attributed to a decreased mass of brown adipose tissue since both the cervical and interscapular depots from obese rats weighed significantly more than did those from lean rats.