Modification of the macaque's vestibulo-ocular reflex by picrotoxin.
The vestibulo-ocular reflex (VOR) in the macaque was tested by a modified Bárány spinning test before and after subcutaneous administration of 1 mg/kg of picrotoxin. The drug caused a decrease in the nystagmus time constant to a value near that of the cupula and a decrease in mystagmus asymmetry. Picrotoxin prevented diazepam from increasing the time constant of vestibular nystagmus. Furthermore, picrotoxin reduced the nystagmus time constant after vermisectomy, a lesion that increases the nystagmus time constant and prevents some VOR modifications. Because picrotoxin and diazepam interact antagonistically in the gamma-aminobutyric acid (GABA) neurotransmitter system, these results show a role of GABA in the neural network that transforms a short cupula time constant into a longer nystagmus time constant.
D000818:Animals; D002531:Cerebellum / Q000502:physiology; D003975:Diazepam / Q000494:pharmacology; D004336:Drug Antagonism; D004585:Electrooculography; D005133:Eye Movements / Q000187:drug effects*; D008251:Macaca; D010852:Picrotoxin / Q000494:pharmacology*; D005680:gamma-Aminobutyric Acid / Q000502:physiology
D003975:Diazepam; D010852:Picrotoxin; D005680:gamma-Aminobutyric Acid