The effect of lithium on amphetamine-induced locomotor stimulation |
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Authors: | Berggren Ulf Tallstedt Leif Ahlenius Sven Engel Jörgen |
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Institution: | (1) Psychiatric Research Center, University of Uppsala, Ulleråker Hospital, S-750 17 Uppsala, Sweden |
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Abstract: | Rats were treated chronically with -methyl-p-tyrosine methyl-ester HCl ( -MT) twice daily for 0–14 days. At 1 h after the (last) -MT injection, d-amphetamine sulphate was given and motor activity was measured in an ANIMEX activity meter for 4 h. Amphetamine-induced excitatory and stereotyped behaviour was scored according to a rating scale in a separate experiment. A single dose of -MT markedly reduced the activity response after amphetamine. After 1–3 days of -MT treatment, tolerance to its amphetamine-antagonistic affect started to develop, reaching a maximal degree after 7–14 days. The pattern of the amphetamine response, monophasic in control rats, became biphasic in the -MT tolerant rats with an early (at 0–1 h) and a late (2–4 h) peak of motor activity. The late peak appeared within 3 days, while the early peak appeared after 7 days of -MT treatment. The results on amphetamine-induced excitatory and stereotyped behaviour in essence agreed with the motor-activity data. It is concluded that tolerance to the amphetamine-antagonistic action of -MT is not complete. Its rate of development varies in a complex pattern, indicating the presence of more than one mechanism of tolerance. |
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Keywords: | -Methyl-p-tyrosine" target="_blank">gif" alt="agr" align="BASELINE" BORDER="0">-Methyl-p-tyrosine Amphetamine Drug tolerance Motor activity |
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