Enhancement of 5-hydroxytryptamine-induced head-twitch response after olfactory bulbectomy.
5-Hydroxytryptamine(2A) receptor agonists evoke the head-twitch response in mice. The head-twitch response in olfactory bulbectomized mice elicited by the administration of 5-hydroxytryptamine (40 microgram/mouse, i.c.v.) was increased about threefold as compared with controls on the 14th day after the operation. The injection of ketanserin (1 mg/kg, i.p.), a 5-hydroxytryptamine(2A) receptor antagonist, inhibited this enhancement of 5-hydroxytryptamine-induced head-twitch response after olfactory bulbectomized. On the 14th day, the number of head-twitch response induced by 5-hydroxytryptophan (40, 80 and 160 mg/kg, i.p.), a precursor of 5-hydroxytryptamine, did not differ between olfactory bulbectomized and control mice. Monoamine oxidase-B activity in the forebrain of olfactory bulbectomized mice was higher than that in controls while monoamine oxidase-A activities were unchanged. The 5-hydroxytryptamine uptake into synaptosomes in the forebrain homogenates of olfactory bulbectomized mice was lower than that in controls. These findings indicate that olfactory bulbectomized causes the enhancement of head-twitch response by a supersensitivity of 5-hydroxytryptamine(2A) receptors in cerebral cortex derived from degeneration of neurons projecting from the olfactory bulb.
Nakagawasai
O
O
Department of Pharmacology, Tohoku Pharmaceutical University, Komatsushima, Aoba-ku, 981-8558, Sendai, Japan. osamun@tohoku-pharm.ac.jp
Tadano
T
T
Arai
Y
Y
Hozumi
S
S
Oba
A
A
Tan-No
K
K
Yasuhara
H
H
Kisara
K
K
Oreland
L
L
D006916:5-Hydroxytryptophan / Q000494:pharmacology; D000818:Animals; D002540:Cerebral Cortex / Q000187:drug effects / Q000378:metabolism*; D003714:Denervation; D004305:Dose-Response Relationship, Drug; D007650:Ketanserin / Q000494:pharmacology; D008297:Male; D051379:Mice; D008995:Monoamine Oxidase / Q000378:metabolism; D009068:Movement / Q000187:drug effects / Q000502:physiology; D009410:Nerve Degeneration / Q000378:metabolism / Q000503:physiopathology; D009830:Olfactory Bulb / Q000166:cytology* / Q000293:injuries / Q000503:physiopathology; D009833:Olfactory Pathways / Q000166:cytology* / Q000293:injuries / Q000503:physiopathology; D044402:Receptor, Serotonin, 5-HT2A; D011985:Receptors, Serotonin / Q000187:drug effects / Q000378:metabolism*; D012018:Reflex / Q000187:drug effects / Q000502:physiology*; D012701:Serotonin / Q000378:metabolism* / Q000494:pharmacology; D012702:Serotonin Antagonists / Q000494:pharmacology; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology*; D015854:Up-Regulation / Q000502:physiology
D044402:Receptor, Serotonin, 5-HT2A; D011985:Receptors, Serotonin; D012702:Serotonin Antagonists; D012701:Serotonin; D007650:Ketanserin; D006916:5-Hydroxytryptophan; D008995:Monoamine Oxidase