TRANSCRANIAL MAGNETIC MOTOR EVOKED-POTENTIALS IN SEDATED DOGS

Transcranial magnetic motor evoked potentials (TMMEP) were obtained in normal sedated dogs. Forms of sedation evaluated were (1) xylazine an d methadone, (2) acepromazine and methadone, (3) medetomidine and meth adone, and (4) droperidol and fentanyl. Stimuli were delivered first w ith the current in the coil flowing in counter-clockwise direction, th en with the current in the coil flowing in clockwise direction. TMMEP were recorded from the extensor carpi radialis muscles of the thoracic limbs and from the cranial tibial muscles of the pelvic limbs. Onset latencies and peak-to-peak amplitudes of the TMMEP were compared for t he four forms of sedation to see which drug combination allowed a reco rding of TMMEP with the shortest latencies and the highest amplitudes. Onset latencies and peak-to-peak amplitudes of the TMMEP were also co mpared to see if there were differences between stimulation with the c urrent in the coil flowing in counter-clockwise or in clockwise direct ion. All forms of sedation allowed recording of TMMEP. Droperidol and fentanyl and acepromazine and methadone sedation were considered super ior to xylazine and methadone and to medetomidine and methadone, becau se they produced TMMEP with significantly shorter latencies (droperido l and fentanyl only) and significantly higher amplitudes (both droperi dol and fentanyl and acepromazine and methadone). No differences were found between stimulation with the current in the coil flowing in coun ter-clockwise or in clockwise direction.