Related Experiment Videos
Methamphetamine-induced changes in activity and water intake during light and dark cycles in rats
T Kita1, M Takahashi, G C Wagner
1Department of Pharmacology, Nara Medical University, Japan.
Abstract:
1. The authors investigated the ambulatory activity and water intake of rats during each 12 hr light and dark cycle for one week following four s.c. injections of 4 or 8 mg/kg of methamphetamine (METH). 2. Administration of the higher METH dose caused an increase in activity during the dark cycle on days 1 through 6 with the maximal increase on day 3 while the increase in activity during the light cycle was observed only on day 1. 3. Water intake increased the first day after administration of both METH doses, but returned to baseline by day 3. 4. Administration of both METH doses induced hyperthermia and the 8 mg/kg dose produced depletions of striatal dopamine and striatal, hippocampal and hypothalamic serotonin on day 3 but only in hippocampal serotonin by day 7. 5. These results demonstrate that high doses of METH produce a long-lasting increase in activity during the dark cycle and a transient increase in water intake. The behavioral changes which occurred during the dark cycle appear to be related to the depletion of central dopamine and/or serotonin.
Insights
High doses of methamphetamine (METH) increase rat activity, particularly in the dark cycle, and transiently affect water intake. These behavioral changes correlate with dopamine and serotonin depletions.
Area of Science:
- Neuroscience
- Pharmacology
- Behavioral Science
Background:
- Methamphetamine (METH) is a psychostimulant with known effects on motor activity and neurotransmitter systems.
- Understanding the long-term behavioral and neurochemical consequences of METH administration is crucial for addiction research.
Purpose of the Study:
- To investigate the effects of repeated methamphetamine administration on ambulatory activity and water intake in rats.
- To examine the neurochemical changes, specifically dopamine and serotonin levels, following METH exposure.
Main Methods:
- Rats received four subcutaneous injections of methamphetamine (4 or 8 mg/kg).
- Ambulatory activity and water intake were monitored across light and dark cycles for one week.
- Neurotransmitter levels (dopamine, serotonin) in striatum, hippocampus, and hypothalamus were analyzed.
Main Results:
- The higher METH dose (8 mg/kg) significantly increased dark cycle activity for six days, peaking on day 3.
- A transient increase in water intake was observed on day 1 post-METH for both doses.
- Hyperthermia was induced by both doses, and significant depletions in striatal dopamine and serotonin were noted by day 3, with hippocampal serotonin depleted by day 7.
Conclusions:
- High-dose methamphetamine induces prolonged increases in dark cycle activity and short-term changes in water intake.
- Observed behavioral alterations are likely linked to METH-induced depletion of central dopamine and/or serotonin.