Dexmedetomidine reduces seizure threshold during enflurane anaesthesia in cats

Dexmedetomidine is an alpha 2 agonist and has been reported to haveproconvulsant actions. To investigate the interaction of dexmedetomidinewith convulsant anaesthetics, we studied effects on seizure threshold incats during enflurane anaesthesia. Cats were prepared with chronicimplantation of electrodes for recording of the corticalelectroencephalogram (EEG) and midbrain reticular formation multi-unitactivity (R-MUA). Seizure threshold, the reciprocal of the number ofelectrical stimuli required to induce generalized EEG seizure activity x1000 (seizure induction index (SII)), was assessed. The effects ofdexmedetomidine 1, 10 and 100 micrograms kg-1 i.v. and yohimbine 500micrograms kg-1, an alpha 2 antagonist, on SII during 3.5% enfluraneanaesthesia were investigated. Dexmedetomidine significantly increased SIIat 10 and 100 micrograms kg-1, and this effect was reversed by yohimbine.We found that high-dose dexmedetomidine reduced seizure threshold duringenflurane anaesthesia.