Imidazoline I1 receptor-mediated reduction of muscle rigidity in the reserpine-treated murine model of Parkinson's disease

To explore the therapeutic potential of imidazoline I1 receptor ligands in motor dysfunction related to the basal ganglia, rigidity was induced in mice by intraperitoneal administration of reserpine. The imidazoline I1 receptor agonists moxonidine and tizanidine reduced rigidity in a dose-dependent manner. Although rigidity was reduced by efaroxan (an imidazoline I1 receptor and α2-adrenoceptor antagonist) and idazoxan (an imidazoline I1 and I2 receptor and α2-adrenoceptor antagonist), SKF86466 and yohimbine, both of which are α2-adrenoceptor antagonists with no affinity for imidazoline receptors, also suppressed rigidity, suggesting that activation rather than blockade of imidazoline I1 receptors contributes to reduction of reserpine-induced muscle rigidity.