title: Unilateral lesions of mesostriatal dopaminergic pathway alters the withdrawal response of the rat hindpaw to mechanical stimulation.
abstract: To investigate the role mesostriatal dopamine system plays in pain processing, we examined the withdrawal response of rat hindpaws to mechanical stimulus at 1, 4, and 12 weeks after unilateral 6-hydroxydopamine (6-OHDA) lesions of the mesostriatal pathway. In all of the 6-OHDA rats examined, almost no tyrosine hydroxylase (TH) immunoreactivity was detected in the substantia nigra, ventral tegmental area, and striatum ipsilateral to 6-OHDA lesions. Alteration in the withdrawal response in this model animal was evaluated by comparing the latency of withdrawal reflex following the mechanical stimulus to the hindpaw. The latency of withdrawal response in the 6-OHDA rats was significantly reduced in the side ipsilateral to 6-OHDA lesions at all times observed, whereas that was not changed through the period observed in the contralateral side, indicating that dopamine depletion in the mesostriatal system has the influence on withdrawal response to the mechanical stimulus. These results show that the unilateral dopamine depletion causes hypersensitivity to the mechanical stimulus in the ipsilateral side, suggesting that, at least in part, dopamine in the mesostriatal system may be involved in sensory processing including pain sensation induced by mechanical stimulation.
authors.affiliation: Department of Psychiatry, Miyazaki Medical College, University of Miyazaki, Miyazaki 889-1692, Japan.
authors.forename: Ryuichiro
authors.initials: R
authors.lastname: Takeda
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Ikeda
authors.forename: Fumiko
authors.initials: F
authors.lastname: Tsuda
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Abe
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Hashiguchi
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Ishida
authors.forename: Toshikazu
authors.initials: T
authors.lastname: Nishimori
mesh_terms: D018663:Adrenergic Agents / Q000633:toxicity; D000818:Animals; D003342:Corpus Striatum / Q000293:injuries / Q000502:physiology*; D004298:Dopamine / Q000378:metabolism*; D007839:Functional Laterality; D006614:Hindlimb / Q000502:physiology; D007150:Immunohistochemistry; D008297:Male; D009434:Neural Pathways / Q000502:physiology*; D016627:Oxidopamine / Q000633:toxicity; D010146:Pain / Q000503:physiopathology*; D010812:Physical Stimulation; D051381:Rats; D017208:Rats, Wistar; D014446:Tyrosine 3-Monooxygenase / Q000378:metabolism
chemical_list: D018663:Adrenergic Agents; D016627:Oxidopamine; D014446:Tyrosine 3-Monooxygenase; D004298:Dopamine