An analysis of the effects of systemically administered clonidine on the food and water intake of rats.

1 It is known that intracerebral injections of clonidine can induce eating in rats but it has not been clear whether systemic administration can produce similar effects. 2 Subcutaneous injections of clonidine (0.01, 0.03, 0.1 mg/kg) increased food and water intake during the 6 h period following injection in non-deprived male rats. 3 Pretreatment with a dose of yohimbine (1.0 mg/kg) shifted the clonidine dose-response curves to the right, suggesting competitive antagonism. 4 A dose of naloxone (0.1 mg/kg) produced a lowering of the clonidine dose-response curve but statistical analysis suggested that the opiate antagonist did not produce a competitive antagonism of the effect of clonidine. 5 The results are consistent with a role for alpha 2-adrenoceptors in appetite regulation.