An electrographic characterization of ketamine-induced linguopharyngeal motor activity

Ketamine-induced buccolinguopharyngeal motor activity was studied in rats visually and by means of force displacement transduction of tongue retrusions, electromyogram (EMG) of motor units of tongue muscles, and pressure transduction of swallowing acts. Each animal was anesthetized with an intramuscular injection of ketamine hydrochloride (100 mg/kg body weight). Through a tracheotomy the airway was intubated and the animal was mounted on a stereotaxic frame in a supine position for monitoring of the above parameters. Four varieties of events were demonstrated: (a) swallowing acts followed by tongue retrusion, (b) tongue retrusions in isolation, (c) tongue retrusions followed by swallowing events, and (d) swallowing events in isolation. All four types of events were vulnerable to intramuscular injection of haloperidol 0.75-2.5 mg/kg within 5 to 10 min and the suppression endured for at least several hours. We conclude that there is a parallel between ketamine-induced oral motor activity and neuroleptic-induced dyskinesia in that both are temporarily suppressed by neuroleptic drugs.