Strain differences in the reverse tolerance to methamphetamine and changes in catecholaminergic neurons in mice.
The effect of methamphetamine (MAP) on ambulatory activity and neurochemical changes in catecholaminergic neurons in the brain were investigated in dd and C57BL/6 strains of male mice. The mice were given repeatedly MAP at 2 mg/kg, s.c., 10 times at a fixed interval of 4 days. Single MAP markedly increased the ambulatory activity in both strains of mice. The ambulation-increasing effect was progressively enhanced without accompanying stereotyped behaviors when the drug was repeatedly given. The dd mice showed higher susceptibility not only to single MAP but also to the enhancing effect of the drug (reverse tolerance) that the C57BL/6 mice. On the other hand, non-treated dd mice exhibited lower maximum densities of 3H-spiperone binding sites in the striatum and 3H-WB4101 binding sites in the cortex and hippocampus than non-treated C57BL/6 mice. In contrast, the dd mice exhibited higher noradrenaline turnover than the C57BL/6 mice in the brain regions examined. The repeated administration of MAP produced decrease in the densities of both 3H-spiperone and 3H-WB4101 binding sites in the corresponding regions with increase in catecholamine turnover in dd mice. However, the similar changes were observed only in 3H-WB4101 binding sites and noradrenaline turnover in C57BL/6 mice. These results suggest that the ambulation-increasing effect of MAP is positively correlated with catecholamine turnover, while it was correlated negatively with the densities of catecholamine binding sites. Furthermore, the enhancing effect of MAP is supposed to have been partially elicited by changes in brain catecholaminergic systems, in particular an increase in catecholamine turnover.(ABSTRACT TRUNCATED AT 250 WORDS)
Hayashi
T
T
Behavioral Research Institute, Gunma University School of Medicine, Maebashi, Japan.
Hirabayashi
M
M
Tadokoro
S
S
D000818:Animals; D001921:Brain / Q000187:drug effects* / Q000378:metabolism; D002395:Catecholamines / Q000378:metabolism*; D008297:Male; D008694:Methamphetamine / Q000494:pharmacology*; D051379:Mice; D008810:Mice, Inbred C57BL; D008815:Mice, Inbred Strains; D009043:Motor Activity / Q000187:drug effects*; D009474:Neurons / Q000187:drug effects; D011869:Radioligand Assay; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects; D011954:Receptors, Dopamine / Q000187:drug effects; D013045:Species Specificity
D002395:Catecholamines; D011942:Receptors, Adrenergic, alpha; D011954:Receptors, Dopamine; D008694:Methamphetamine