Effects of mu receptor agonists and droperidol on motor coordination in mice.

The effects of morphine, fentanyl, sufentanil and droperidol on motor coordination in mice were studied. Animals were trained to complete successfully the rotarod test before assessing the effects of drugs. Administration of analgesic doses of the mu agonists morphine, fentanyl and sufentanil did not inhibit motor coordination. Droperidol produced a dose related inhibition of motor coordination. When a subthreshold dose of droperidol was administered followed by an opiate, a significant inhibition of motor coordination was observed. The results indicate that although analgesic doses of mu opioid agonists do not affect motor coordination, their combination with droperidol results in motor incoordination. The mechanisms and/or opioid receptor sub-types involved in this in vivo interaction remain to be established.