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Delay in the recovery of normal sleep-wake cycle after disruption of the light-dark cycle in mice: a bipolar disorder-prone animal model?

Jung SH, Park JM, Moon E, Chung YI, Lee BD, Lee YM, Kim JH, Kim SY, Jeong HJ - Psychiatry Investig (2014)

Bottom Line: During the dark cycle on the 16th experimental day, their general locomotor activities were measured in an open field for 120 minutes after an injection of quinpirole (0.5 mg/kg, s.c.).The individual differences in the recovery rate of the baseline sleep-wake cycle were noted after 3 days of switching the LD cycle.Given that the quinpirole-induced hyperactivity is an animal model of bipolar disorder, our results suggest individuals who have difficulties in recovery from circadian rhythm disruption may be vulnerable to bipolar disorder.

View Article: PubMed Central - PubMed

Affiliation: Department of Psychiatry, Pusan National University Hospital, Busan, Republic of Korea.

ABSTRACT

Objective: Disruption of the circadian rhythm is known as a provoking factor for manic episodes. Individual differences exist in the recovery rate from disruption in the general population. To develop a screening method to detect individuals vulnerable to bipolar disorder, the authors observed the relationship between the recovery of the normal sleep-wake cycle after switching the light-dark (LD) cycle and quinpirole-induced hyperactivity in mice.

Methods: Sixteen male mice (age of 5 weeks, weight 28-29 gm) were subjected to a circadian rhythm disruption protocol. Sleep-wake behaviors were checked every 5 min for a total duration of 15 days, i.e., 2 days of baseline observations, 3 days of LD cycle changes, and 10 days of recovery. During the dark cycle on the 16th experimental day, their general locomotor activities were measured in an open field for 120 minutes after an injection of quinpirole (0.5 mg/kg, s.c.).

Results: The individual differences in the recovery rate of the baseline sleep-wake cycle were noted after 3 days of switching the LD cycle. Fifty percent (n=8) of the mice returned to the baseline cycle within 6 days after normalizing the LD cycle (early recovery group). The locomotor activities of mice that failed to recover within 6 days (delayed recovery group) were significantly higher (mean rank=12.25) than those of the early recovery group (mean rank=4.75, u=62.0, p=0.001, Mann-Whitney U test).

Conclusion: Given that the quinpirole-induced hyperactivity is an animal model of bipolar disorder, our results suggest individuals who have difficulties in recovery from circadian rhythm disruption may be vulnerable to bipolar disorder.

No MeSH data available.


Related in: MedlinePlus

Sleep-wake patterns observed by a circadian rhythm disruption protocol. White bar: light cycle, Black bar: dark cycle, Gray bar: dark cycle during disruption phase. A: from 8:00 A.M. to 8:00 P.M., P: from 8:00 P.M. to 8:00 A.M. of the day after. Blue line: early recovery group, Red line: delayed recovery group.
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Figure 1: Sleep-wake patterns observed by a circadian rhythm disruption protocol. White bar: light cycle, Black bar: dark cycle, Gray bar: dark cycle during disruption phase. A: from 8:00 A.M. to 8:00 P.M., P: from 8:00 P.M. to 8:00 A.M. of the day after. Blue line: early recovery group, Red line: delayed recovery group.

Mentions: The sleep patterns of the light-dark cycle for 15 days are shown in Figure 1. Every sleep-wake pattern was compared to reveal the moment at which fifty percent of the mice returned to the baseline cycle. Fifty percent (n=8) of the mice returned to the baseline cycle in 6 days after normalization of the light-dark cycle, and they were divided into two groups according to the total sleep duration of dark period on the 6th day after normalizing the light-dark cycle. Considering that mice are nocturnal animals, we named the lower 50% group as the early recovery group (n=8) and the upper 50% group as the delayed recovery group (n=8). Mann-Whitney U test was used to compare the distribution of locomotor activities for 120 minutes. All statistical analyses were performed using the Statistical Package for Social Science for Windows, version 18.0 and the level of statistical significance was set at p<0.05.


Delay in the recovery of normal sleep-wake cycle after disruption of the light-dark cycle in mice: a bipolar disorder-prone animal model?

Jung SH, Park JM, Moon E, Chung YI, Lee BD, Lee YM, Kim JH, Kim SY, Jeong HJ - Psychiatry Investig (2014)

Sleep-wake patterns observed by a circadian rhythm disruption protocol. White bar: light cycle, Black bar: dark cycle, Gray bar: dark cycle during disruption phase. A: from 8:00 A.M. to 8:00 P.M., P: from 8:00 P.M. to 8:00 A.M. of the day after. Blue line: early recovery group, Red line: delayed recovery group.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4225215&req=5

Figure 1: Sleep-wake patterns observed by a circadian rhythm disruption protocol. White bar: light cycle, Black bar: dark cycle, Gray bar: dark cycle during disruption phase. A: from 8:00 A.M. to 8:00 P.M., P: from 8:00 P.M. to 8:00 A.M. of the day after. Blue line: early recovery group, Red line: delayed recovery group.
Mentions: The sleep patterns of the light-dark cycle for 15 days are shown in Figure 1. Every sleep-wake pattern was compared to reveal the moment at which fifty percent of the mice returned to the baseline cycle. Fifty percent (n=8) of the mice returned to the baseline cycle in 6 days after normalization of the light-dark cycle, and they were divided into two groups according to the total sleep duration of dark period on the 6th day after normalizing the light-dark cycle. Considering that mice are nocturnal animals, we named the lower 50% group as the early recovery group (n=8) and the upper 50% group as the delayed recovery group (n=8). Mann-Whitney U test was used to compare the distribution of locomotor activities for 120 minutes. All statistical analyses were performed using the Statistical Package for Social Science for Windows, version 18.0 and the level of statistical significance was set at p<0.05.

Bottom Line: During the dark cycle on the 16th experimental day, their general locomotor activities were measured in an open field for 120 minutes after an injection of quinpirole (0.5 mg/kg, s.c.).The individual differences in the recovery rate of the baseline sleep-wake cycle were noted after 3 days of switching the LD cycle.Given that the quinpirole-induced hyperactivity is an animal model of bipolar disorder, our results suggest individuals who have difficulties in recovery from circadian rhythm disruption may be vulnerable to bipolar disorder.

View Article: PubMed Central - PubMed

Affiliation: Department of Psychiatry, Pusan National University Hospital, Busan, Republic of Korea.

ABSTRACT

Objective: Disruption of the circadian rhythm is known as a provoking factor for manic episodes. Individual differences exist in the recovery rate from disruption in the general population. To develop a screening method to detect individuals vulnerable to bipolar disorder, the authors observed the relationship between the recovery of the normal sleep-wake cycle after switching the light-dark (LD) cycle and quinpirole-induced hyperactivity in mice.

Methods: Sixteen male mice (age of 5 weeks, weight 28-29 gm) were subjected to a circadian rhythm disruption protocol. Sleep-wake behaviors were checked every 5 min for a total duration of 15 days, i.e., 2 days of baseline observations, 3 days of LD cycle changes, and 10 days of recovery. During the dark cycle on the 16th experimental day, their general locomotor activities were measured in an open field for 120 minutes after an injection of quinpirole (0.5 mg/kg, s.c.).

Results: The individual differences in the recovery rate of the baseline sleep-wake cycle were noted after 3 days of switching the LD cycle. Fifty percent (n=8) of the mice returned to the baseline cycle within 6 days after normalizing the LD cycle (early recovery group). The locomotor activities of mice that failed to recover within 6 days (delayed recovery group) were significantly higher (mean rank=12.25) than those of the early recovery group (mean rank=4.75, u=62.0, p=0.001, Mann-Whitney U test).

Conclusion: Given that the quinpirole-induced hyperactivity is an animal model of bipolar disorder, our results suggest individuals who have difficulties in recovery from circadian rhythm disruption may be vulnerable to bipolar disorder.

No MeSH data available.


Related in: MedlinePlus