1996 Volume 1 Issue 1 Pages 21-26
The aim of this study is to examine the stereotyped behaviors in animals treated with long-term methamphetamine (MAP) administration, and to clarify the correlation between these behaviors and changes in dopaminergic neuronal activity by immunohistochemistry.
Ten male guinea pigs weighing 300-350g were used as experimental animals. MAP was intraperitoneally injected into animals at a dose of 10 mg/kg/day for 15 weeks. As a control group, ten animals were injected with normal saline solution. After observations on the behaviors for 15 weeks, all animals were subjected to the immunohistochemical examination for dopaminergic neuronal activity. Cryostat sections (20 μ m) obtained from the striatum, the substantia nigra and the ventral tegmental area were incubated with polyclonal anti-dopamine (DA) antibody.
Body weight of MAP-treated animal was significantly lower than that of control animal after 7 weeks of administration period. The stereotyped behaviors including biting, turning, rearing, jumping and head-weaving were observed in MAP-treated animals. Biting was the most popular behavior observed in MAP-treated animals and was found in all animals immediately after the administration of MAP, while other behaviors were frequently observed in MAP-treated animals in the latter half of administration period. DA-immunostainability in neurons of the substantia nigra in MAP-treated animals showed an obvious decrease compared with that in control animals.
In this study, the long-term MAP administration decreased a DA level of neurons in the substantia nigra and induced the stereotyped behaviors in the latter period of administration. It is considered that the neurochemical changes in the nigrostriatal tract may correlate to the appearance of the stereotyped behaviors.
