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Effect of light/dark cycle alteration on morphine-induced conditioned place preference
Pouya Tahsili-Fahadan1, Noushin Yahyavi-Firouz-Abadi, Mohammad Hossein Ghahremani
1Department of Pharmacology, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran. dehpour@medscape.com
Neuroreport
|December 1, 2005
Summary
Light/dark cycle alterations affect morphine-induced conditioned place preference in mice. Melatonin administration and photoperiod changes can modulate this effect, influencing drug-associated learning.
Area of Science:
- Neuroscience
- Chronobiology
- Pharmacology
Background:
- Conditioned place preference (CPP) is a behavioral model used to study drug reward.
- Light/dark cycles (photoperiods) can influence circadian rhythms and behavior.
Purpose of the Study:
- To investigate the impact of altered light/dark cycles on morphine-induced CPP in mice.
- To examine the modulatory role of melatonin in this context.
Main Methods:
- Mice were exposed to different light/dark cycle durations (12/12, 6/18, 18/6 hours).
- Morphine was administered to induce CPP.
- Melatonin was administered chronically and acutely.
- Acute photoperiod shifts were also tested.
Main Results:
- Morphine induced CPP across different light/dark cycles, but dose-dependently.
- A 6/18 light/dark cycle required higher morphine doses for CPP.
- Chronic melatonin treatment abolished CPP in the 18/6 cycle.
- Acute photoperiod changes and acute melatonin administration modulated CPP.
Conclusions:
- Light/dark cycle duration significantly influences morphine-induced CPP.
- Melatonin plays a role in modulating the rewarding effects of morphine.
- Circadian rhythm disruption impacts drug-associated learning and reward.
