Involvement of the fimbria fornix in the initiation but not in the expression of methamphetamine-induced sensitization.
To put forward our previous finding that the lesion of the fimbria fornix, a hippocampo-accumbal pathway, blocked the development of behavioral sensitization induced by repeated methamphetamine (MAP) administrations, we examined the role of the fimbria fornix in the expression of sensitization in this study. After rats had shown locomotor augmentation following repeated drug injections, they received either the fimbria fornix lesion or a sham operation. Both groups of rats still exhibited a similar sensitized locomotor response to MAP as before the surgeries. In addition, we evaluated dopamine metabolism in the nucleus accumbens of these rats following a challenge injection of MAP after the behavioral study. The data obtained correspond to the results of behavioral experiments in that 3-methoxytyramine, one of the dopamine metabolites, increased significantly after MAP challenge only in the groups of sensitized animals. These findings further support the recent concept that there may exist different neural mechanisms in the initiation and expression of sensitization phenomenon.
Yoshikawa
T
T
Department of Neuropsychiatry, Tokyo Medical and Dental University, Japan.
Watanabe
A
A
Shibuya
H
H
Toru
M
M
D015102:3,4-Dihydroxyphenylacetic Acid / Q000378:metabolism; D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects*; D004298:Dopamine / Q000378:metabolism; D006624:Hippocampus / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D006719:Homovanillic Acid / Q000378:metabolism; D008297:Male; D008694:Methamphetamine / Q000494:pharmacology*; D008781:Methyltyrosines / Q000378:metabolism; D009043:Motor Activity / Q000187:drug effects; D009434:Neural Pathways / Q000502:physiology; D009714:Nucleus Accumbens / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar
D008781:Methyltyrosines; D015102:3,4-Dihydroxyphenylacetic Acid; C032745:methyl-3-tyrosine; D008694:Methamphetamine; D004298:Dopamine; D006719:Homovanillic Acid