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Combined effects of methamphetamine and morphine on ambulatory activity in mice and continuous avoidance response in
Abstract:
Combined effects of methamphetamine and morphine were investigated by means of ambulatory activity in mice and continuous avoidance response in rats. Single administration of methamphetamine (0.5-2 mg/kg sc) or morphine (2.5-10 mg/kg sc) increased the ambulatory activity in a dose-dependent manner. The ambulation-increasing effect of methamphetamine and morphine were synergistic throughout the combined doses tested. Methamphetamine (0.13 and 0.5 mg/kg sc) produced an increase in frequency of lever-pressing and a decrease in shock rate, showing facilitation of the avoidance response, in a dose-dependent manner. Morphine tended to facilitate the avoidance response at lower doses (1.3 and 2.5 mg/kg sc), whereas, at higher doses (5 and 10 mg/kg sc), it elicited decrease in the frequency of lever-pressing and increase in the shock rate, showing suppressing of the avoidance response. The avoidance-facilitating effect of methamphetamine was attenuated by higher doses of morphine. The present results suggest that combined administration of methamphetamine and morphine shows synergistic effect on ambulatory activity in mice, and synergistic and antagonistic effects on the avoidance response in rats depending on the doses combined.
Insights
This study reveals that combining methamphetamine and morphine synergistically increases ambulatory activity in mice. However, their combined effect on avoidance response in rats is dose-dependent, showing both synergistic and antagonistic interactions.
Area of Science:
- Neuroscience
- Pharmacology
- Behavioral Science
Background:
- Methamphetamine and morphine are commonly used psychoactive substances.
- Understanding their combined effects is crucial for predicting behavioral outcomes.
Purpose of the Study:
- To investigate the synergistic and antagonistic effects of combined methamphetamine and morphine administration.
- To analyze the impact on ambulatory activity in mice and avoidance response in rats.
Main Methods:
- Animals were administered varying doses of methamphetamine and morphine via subcutaneous injection.
- Ambulatory activity was measured in mice.
- Continuous avoidance response was assessed in rats, monitoring lever-pressing frequency and shock rate.
Main Results:
- Both methamphetamine and morphine dose-dependently increased ambulatory activity in mice, with synergistic effects when combined.
- Methamphetamine facilitated avoidance response in rats, while morphine showed biphasic effects (facilitation at low doses, suppression at high doses).
- High doses of morphine attenuated the avoidance-facilitating effects of methamphetamine in rats.
Conclusions:
- Combined methamphetamine and morphine exhibit synergistic effects on ambulatory activity in mice.
- The interaction between methamphetamine and morphine on avoidance response in rats is complex, displaying both synergistic and antagonistic properties contingent on dosage.