Neurochemical and behavioral effects of clonidine and related imidazolines: interaction with alpha-adrenoceptors.

Clonidine and other imidazolines, including phentolamine, inhibited the norepinephrine-elicited accumulation of cyclic AMP in brain slices via blockade or postsynpatic alpha-adrenoceptors. Clonidine (0.0125--0.050 mg/kg, i.p.) antagonized the increase in locomotor activity induced by amphetamine in a dose-dependent manner. It is suggested that the common ability of clonidine and phentolamine to antagonize norepinephrine-stimulated accumulation of cyclic AMP provides a possible explanation for the similar behavioral effects of these compounds, including their antagonism of the locomotor effects of amphetamine.