Differential effects of diazepam upon vestibulo- and visual-oculomotor responses in the rabbit

The effects of intravenously administered diazepam (0.6 mg/kg) on vestibulo-ocular reflex (VOR), optokinetic nystagmus (OKN), optovestibular reflex (OVR) and their after-nystagmus were examined in rabbits. These reflexes were evoked by velocity step of 20 degrees/sec of chair or drum rotation. Slow phase eye velocity (SPEV) of OVR shows algebraic summation of those of VOR and OKN. Although SPEVs of VOR, OKN and OVR significantly decreased at 10 and 30 min after diazepam injection (p less than 0.05, t-test), OKN shows most distinctive reduction. SPEV reduction of OVR after diazepam administration was also equal to the algebraic summation of VOR and OKN reductions.