Excitatory and inhibitory effects of 5-hydroxytryptamine on the firing rate of medial vestibular nucleus neurons in the rat.
The effects of microiontophoretic application of 5-hydroxytryptamine (5-HT) on the neuronal firing rate of the medial vestibular nucleus (MVN) were studied in anaesthetized rats. Ninety-three % of the units modified their background activity following 5-HT iontophoresis, enhancements of the firing rate being recorded in 42%, decreases in 38% and biphasic effects in 13%. 5-HT antagonists methysergide and ketanserin blocked the excitatory but not the inhibitory responses to 5-HT. These latter were, however, mimicked by 5-HT agonists 5-methoxy-N,N-dimethyltryptamine (5MeODMT) and 8-hydroxy-2(di-n-propyl-amino)tetralin (8-OH-DPAT). It is concluded that 5-HT can variously influence the background activity of MVN neurons and that 5-HT2 and probably 5-HT1A receptors are involved in the responses.
Licata
F
F
Istituto di Fisiologia umana, Università di Catania, Italy.
Li Volsi
G
G
Maugeri
G
G
Santangelo
F
F
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D004558:Electric Stimulation; D007478:Iontophoresis; D008297:Male; D009474:Neurons / Q000187:drug effects* / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar; D011985:Receptors, Serotonin / Q000187:drug effects; D012701:Serotonin / Q000494:pharmacology*; D012702:Serotonin Antagonists / Q000494:pharmacology; D017366:Serotonin Receptor Agonists / Q000494:pharmacology; D014726:Vestibular Nuclei / Q000166:cytology / Q000187:drug effects* / Q000502:physiology
D011985:Receptors, Serotonin; D012702:Serotonin Antagonists; D017366:Serotonin Receptor Agonists; D012701:Serotonin