Suppressive action of picrotoxin, a gaba antagonist, On labyrinthine spontaneous nystagmus and vertigo in man

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Abstract
GABA evidently acts as the excitatory neurotransmitter at synapses between vestibular hair cells and the afferent fibers in the human labyrinth. Vestibular dysfunctions such as labyrinthine vertigo were studied in patients by influencing the peripheral GABA system with the GABA-antagonist picrotoxin, a well known analeptic drug. With the application of slow infusion rates of only milligrams of picrotoxin a distinct suppression of peripheral spontaneous nystagmus, caloric excitability of labyrinths and labyrinthine vertigo, without general CNS-induced arousal effect, were observed. A latent central spontaneous nystagmus can become manifest, whereas a manifest central spontaneous nystagmus remains unchanged. A future application of picrotoxin as a diagnostic and therapeutic tool in cases involving vestibular disorders is discussed.