Neurotransmitters of vestibular commissural inhibition in the cat.
The present study examined transmitters that regulate commissural inhibition. Extracellular spikes of a single vestibular neuron were recorded in decerebrated cats. Multibarreled electrodes were filled with transmitter candidates (GABA and glycine), their specific antagonists (bicuculline, strychnine) and 2 M NaCl for extracellular recording. After isolation of a type I neuron, chemicals were iontophoretically applied to examine their effects on the activity of the neuron. The results were as follows. Commissural inhibition caused by electrical stimulation of the contralateral labyrinth was not abolished by the application of strychnine (a glycine antagonist), but was abolished by bicuculline (a GABA antagonist). Commissural inhibition was not abolished by phaclofen. Some bicuculline-sensitive neurons, with a short-latency commissural inhibition (presumably disynaptic inhibition), showed spacial summation when the conditioning stimulation (contralateral vestibular nerve stimulation) was applied with the test stimulation (vestibular nucleus stimulation). It was concluded that commissural inhibition was activated by the GABAA receptor, but not by the GABAB receptor, that the inhibitory type I neurons located in the contralateral vestibular nucleus were GABAergic, and that inhibitory type II neurons were also GABAergic neurons.
Furuya
N
N
Department of Otolaryngology, Teikyo University School of Medicine, Ichihara Hospital, Chiba, Japan.
Koizumi
T
T
D000818:Animals; D002415:Cats; D004292:Dominance, Cerebral / Q000502:physiology*; D004558:Electric Stimulation; D005998:Glycine / Q000502:physiology; D008564:Membrane Potentials / Q000502:physiology; D009433:Neural Inhibition / Q000502:physiology*; D009474:Neurons / Q000502:physiology; D018377:Neurotransmitter Agents / Q000502:physiology*; D011930:Reaction Time / Q000502:physiology; D011963:Receptors, GABA-A / Q000502:physiology; D018009:Receptors, Glycine / Q000502:physiology; D014725:Vestibular Nerve / Q000502:physiology*; D014726:Vestibular Nuclei / Q000502:physiology; D005680:gamma-Aminobutyric Acid / Q000502:physiology
D018377:Neurotransmitter Agents; D011963:Receptors, GABA-A; D018009:Receptors, Glycine; D005680:gamma-Aminobutyric Acid; D005998:Glycine