Reserpine-induced rigidity in rats: drug effects on muscle tone from corpus striatum and nucleus accumbens

A study of the pathophysiological mechanisms of reserpine rigidity with the aid of a mechanographic method for the quantification of muscle tone. Apomorphine was used as a test substance to reduce reserpine rigidity by stimulation of dopamine receptors. Some experiments were made with additional drug treatment in an attempt to ascertain the dopaminergic specificity of the test. Apomorphine injected bilaterally to the corpus striatum has been shown to counteract the rigidity [6]. Microinjections of reserpine to corpus striatum induced rigidity with dominance in the hindleg ipsilateral to the side of injection. This rigidity was reduced by subcutaneous apomorphine. The effect of subcutaneous apomorphine on the rigidity was blocked by prior microinjection of trifluoperazine to the corpus striatum. Injections to nucleus accumbens were ineffective in all these respects. It is concluded that reserpine induces rigidity mainly by interference with the dopamine transmission in the corpus striatum.