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Within-day variation in spatial memory deficit induced by scopolamine.
Hiroki Fujitaka1, Akiko Okada, Takayoshi Masuoka
1Department of Medicinal Pharmacology, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama 700-8530, Japan.
Pharmacology
|November 6, 2009
Summary
Scopolamine impairs memory performance, with greater effects during the light period. The suprachiasmatic nucleus (SCN) controls this daily variation in scopolamine
Area of Science:
- Neuroscience
- Chronobiology
- Pharmacology
Background:
- Circadian rhythms influence cognitive functions.
- The suprachiasmatic nucleus (SCN) is the master circadian clock.
- Daily variations in drug efficacy are known but not fully understood.
Purpose of the Study:
- To investigate the effect of scopolamine on radial maze performance.
- To determine if circadian rhythm influences scopolamine-induced memory deficits.
- To assess the role of the SCN in mediating these daily variations.
Main Methods:
- Radial maze task in rats during light and dark periods.
- Administration of scopolamine at varying doses.
- Comparison between sham-operated and SCN-lesioned rats.
Main Results:
- Scopolamine dose-dependently increased memory errors (total, reference, working).
- Memory deficits were more pronounced during the light period compared to the dark period.
- SCN lesioning abolished the difference in scopolamine's effect between light and dark periods.
Conclusions:
- Circadian rhythm, regulated by the SCN, significantly modulates the impact of scopolamine on memory.
- Within-day variations in scopolamine's efficacy are driven by the endogenous circadian system.
- Targeting circadian mechanisms may optimize therapeutic strategies involving cholinergic drugs.
