Cortical control of tongue contractility in the rat under ketamine anaesthesia

1. Cortico-lingual and linguo-cortical interconnectivity was investigated in ketamine-anaesthetized rats mounted onto a stereotaxic apparatus. The tip of the tongue was tied to a force displacement transducer to monitor tongue retrusions. The tongue cortical area was exposed in one or both hemispheres to record evoked potentials or spontaneous electroencephalographic (EEG) activity, or to stimulate electrically with single square pulses of up to 50 V and 0.25 ms pulse width. 2. The results showed that (i) tongue retrusions elicited by electrical stimulation were identical to those induced by ketamine; (ii) ketamine-induced tongue contractions correlated in time with cortical EEG potentials which were easily distinguished from the background noise; (iii) haloperidol (2.5 mg/kg, i.m.) suppressed the cortically evoked tongue contractions as well as the ketamine-induced contractions. 3. These results suggest that ketamine-induced tongue retrusions may involve the cortex in their mediation if not their generation and that this may provide a basis for the suppression of dyskinetic activity during sleep or unconsciousness.