Inhibitory effects of tandospirone, a 5-HT1A agonist, on medial vestibular nucleus neurons responding to lateral roll tilt stimulation in rats.
An electrophysiological study was performed using chloral hydrate-anesthetized rats to determine whether tandospirone, a 5-HT1A agonist, affects neuronal activities of the medial vestibular nucleus (MVN), since serotonergic innervation and 5-HT1A receptors are present in this nucleus. Tandospirone applied microiontophoretically at a current of 20-60 nA caused an inhibition of tilt-induced firing of alpha-type neurons, which showed increased and decreased firing with lateral tilt ipsilateral and contralateral to the recording site, respectively, along with that of beta-type neurons which exhibited the reverse responses to ipsilateral and contralateral tilt stimulation. The inhibition was antagonized during simultaneous, iontophoretic application of WAY-100635 (20-60 nA), a 5-HT1A receptor antagonist, although WAY-100635 alone rarely affected spontaneous or tilt-induced firing in either type of neurons. These results suggest that tandospirone acts on a 5-HT1A receptor to inhibit transmission of otolith information to alpha- and beta-type MVN neurons.
Amano
T
T
Department of Pharmacology, Hiroshima University School of Medicine, Hiroshima 734-8551, Japan.
Akbar
M
M
Matsubayashi
H
H
Sasa
M
M
D000200:Action Potentials / Q000187:drug effects / Q000502:physiology; D000818:Animals; D054833:Isoindoles; D008297:Male; D009433:Neural Inhibition / Q000187:drug effects* / Q000502:physiology; D009474:Neurons / Q000187:drug effects* / Q000378:metabolism; D010812:Physical Stimulation; D010879:Piperazines / Q000494:pharmacology*; D004856:Postural Balance / Q000187:drug effects / Q000502:physiology; D011187:Posture / Q000502:physiology; D011725:Pyridines / Q000494:pharmacology; D011743:Pyrimidines / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D011985:Receptors, Serotonin / Q000187:drug effects* / Q000378:metabolism; D044263:Receptors, Serotonin, 5-HT1; D012399:Rotation; D012701:Serotonin / Q000378:metabolism*; D012702:Serotonin Antagonists / Q000494:pharmacology; D017366:Serotonin Receptor Agonists / Q000494:pharmacology*; D014726:Vestibular Nuclei / Q000187:drug effects* / Q000378:metabolism; D014722:Vestibule, Labyrinth / Q000187:drug effects / Q000502:physiology
D054833:Isoindoles; D010879:Piperazines; D011725:Pyridines; D011743:Pyrimidines; D011985:Receptors, Serotonin; D044263:Receptors, Serotonin, 5-HT1; D012702:Serotonin Antagonists; D017366:Serotonin Receptor Agonists; C055267:tandospirone; D012701:Serotonin; C090413:N-(2-(4-(2-methoxyphenyl)-1-piperazinyl)ethyl)-N-(2-pyridinyl)cyclohexanecarboxamide