Ultradian Rest-activity Rhythms Induced by Quinpirole in Mice Using Wavelet Analysis
Jeonghyun Park1, Eunsoo Moon1,2,3, Hyun Ju Lim1,4, Kyungwon Kim1,2, Hwagyu Suh1,2, Min Yoon3, Jung Hyun Lee5, Yoo Rha Hong5
1Department of Psychiatry and Biomedical Research Institute, Pusan National University Hospital, Busan, Korea
2Department of Psychiatry, Pusan National University School of Medicine, Yangsan, Korea
3Department of Applied Mathematics, Pukyong National University, Busan, Korea
4Department of Psychology, Gyeongsang National University, Jinju, Korea
5Department of Pediatrics, College of Medicine, Kosin University, Busan, Korea
Correspondence to: Eunsoo Moon
Department of Psychiatry and Biomedical Research Institute, Pusan National University Hospital, Pusan National University School of Medicine, 179 Gudeok-ro, Seo-gu, Busan 49241, Korea
E-mail: esmun@hanmail.net
ORCID: https://orcid.org/0000-0002-8863-3413

Yoo Rha Hong
Department of Pediatrics, College of Medicine, Kosin University, 262 Gamcheon-ro, Seo-gu, Busan 49267, Korea
E-mail: pondhong@gmail.com
ORCID: https://orcid.org/0000-0002-7673-070X
Received: December 6, 2023; Revised: February 3, 2024; Accepted: February 28, 2024; Published online: March 15, 2024.
© The Korean College of Neuropsychopharmacology. All rights reserved.

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Objective: Ultradian rhythms are biological rhythms with periods of a few seconds to a few hours. Along with circadian rhythms, ultradian rhythms influence human physiology. However, such rhythms have not been studied as intensively as circadian rhythms. This study aimed to identify ultradian rest-activity rhythms induced by the dopamine D2/D3 agonist quinpirole in mice.
Methods: We used 10 mice from the Institute of Cancer Research. Quinpirole was administered at a dose of 0.5 mg/kg. We assessed free rest-activity using infrared detectors and conducted wavelet analysis to measure the period and its variation. We also used the paired t test to compare ultradian rhythm patterns.
Results: Quinpirole did not significantly change total 24-hour locomotor activity (p = 0.065). However, it significantly increased locomotor activity during the dark phase (p = 0.001) and decreased it during the light phase (p = 0.016). In the continuous wavelet transform analysis, the mean period was 5.618 hours before quinpirole injection and 4.523 hours after injection. The period showed a significant decrease (p = 0.040), while the variation remained relatively consistent before and after quinpirole injection.
Conclusion: This study demonstrated ultradian rest-activity rhythms induced by quinpirole using wavelet analysis. Quinpirole-induced ultradian rhythms exhibited rapid oscillations with shortened periods and increased activity during the dark phase. To better understand these changes in ultradian rhythms caused by quinpirole, it is essential to compare them with the effects of other psychopharmacological agents. Furthermore, investigating the pharmacological impact on ultradian rest-activity rhythms may have valuable applications in clinical studies.
Keywords: Quinpirole; Dopamine; Locomotion; Ultradian rhythm; Circadian rhythm; Wavelet analysis

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