Effects of anti-vertigo drugs on medial vestibular nucleus neurons activated by horizontal rotation.
The effects of anti-vertigo drugs on medial vestibular nucleus (MVN) neurons were examined to assess the site and mode of action using cats anesthetized with alpha-chloralose. Single neuron activity in the MVN was extracellularly recorded using a silver wire microelectrode attached along a seven-barreled micropipette, each of which was filled with diphenhydramine, diphenidol, betahistine, glutamate or NaCl. Type I of the MVN neurons were identified according to the responses obtained when the animal placed on a turn-table was rotated sinusoidally. The effects of the drugs were examined on type I neurons which received impulses primarily from the labyrinth and sent them to the oculomotor nuclei. The microiontophoretic application of diphenhydramine, diphenidol and betahistine inhibited rotation-induced firing of type I MVN neurons. Diphenhydramine and diphenidol were more potent than betahistine. These results suggest that these drugs directly act on MVN neurons to reduce the responsiveness to rotatory stimulation.
Department of Pharmacology, Faculty of Medicine, Kyoto University, Japan.
A
A
Kawabata
M
M
Sasa
T
T
Kishimoto
S
S
Takaori
D000818:Animals; D001621:Betahistine / Q000494:pharmacology; D002415:Cats; D004155:Diphenhydramine / Q000494:pharmacology; D005971:Glutamates / Q000494:pharmacology; D018698:Glutamic Acid; D007478:Iontophoresis; D008297:Male; D009474:Neurons / Q000187:drug effects*; D010880:Piperidines / Q000494:pharmacology; D012399:Rotation; D012965:Sodium Chloride / Q000494:pharmacology; D014717:Vertigo / Q000188:drug therapy*; D014726:Vestibular Nuclei / Q000166:cytology / Q000187:drug effects*
D005971:Glutamates; D010880:Piperidines; D018698:Glutamic Acid; D012965:Sodium Chloride; D004155:Diphenhydramine; C004858:diphenidol; D001621:Betahistine