Effects of cholinergic agonists and antagonists of nucleus vestibularis lateralis unit discharge to vestibular nerve stimulation in the cat.

Unit discharge in nucleus vestibularis (NVL) was studied in locally anesthetized cats. The mean firing rate +/-S.E. of spontaneous unitary discharges of NVL neurons was 19.8+/-0.9 Hz and that of spinal-transected animals was 18.0+/-1.6 Hz. The mean firing rate of these neurons in animals with cerebellum ablation and the administration of scopolamine in a dose of 0.5 mg/kg i.v. was relatively low. After administration of physostigmine in a dose of 25 mug/kg i.v. the firing rate was enhanced. The effects of physostigmine were antagonized by scopolamine. About 95% of NVL neurons activated by single electrical shocks to the ipsilateral vestibular nerve showed regular firing following administration of physostigmine. These neurons changed to a gamma distribution at lambda=2 following administration of scopolamine.