Modulatory roles of GABAergic mechanisms in post-rotatory nystagmus in the rabbit

1. To determine how the GABAergic mechanism operates in the generation of post-rotatory nystagmus, an experiment was performed with GABAergic drugs in rabbits. 2. Subconvulsive doses of picrotoxin (0.3-0.6 mg/kg, i.v.) and bicuculline (0.1 mg/kg, i.v.) decreased the number of post-rotatory nystagmus beats, whereas strychnine sulphate, at a subconvulsive dose (0.1 mg/kg i.v.), increased it. 3. Diazepam (1 mg/kg, i.v.) remarkably increased the number of post-rotatory nystagmus beats. Pretreatment with picrotoxin (0.45 mg/kg, i.v.), bicuculline (0.1 mg/kg, i.v.) or semicarbazide-HCl (180 mg/kg, i.v.) antagonized the effects of diazepam (1 mg/kg, i.v.). 4. GABAergic mechanisms may play a modulatory role in the production of nystagmus rhythm. Strychnine-sensitive neurons involved in the vestibular mechanism may behave in a different manner from picrotoxin-sensitive neurons.