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

Abstract

There is evidence that GABA acts as the excitatory neurotransmitter at synapses between vestibular hair cells and the afferent fibres in the mammalian labyrinth. The question arose as to whether certain vestibular dysfunctions such as labyrinthine vertigo could be treated in patients by influencing the peripheral GABA system by means of 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, was 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.