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Circadian rhythmicity in serotonin transporter knockout mice
Raina D Pang1, Daniel P Holschneider2, Joseph D Miller3
1Graduate Program in Neuroscience, University of Southern California, United States.
Life Sciences
|August 14, 2012
Summary
Mice lacking the serotonin transporter (5-HTT KO) showed normal circadian rhythms but had a reduced response to light-induced phase shifts. This suggests serotonin
Area of Science:
- Neuroscience
- Chronobiology
- Behavioral Genetics
Background:
- Serotonin transporter knockout (5-HTT KO) mice display heightened serotonin levels and depressive-like behaviors.
- Disruptions in circadian rhythms are linked to mood disorders.
- Investigating circadian rhythmicity in 5-HTT KO mice is crucial for understanding mood regulation.
Purpose of the Study:
- To test the hypothesis that 5-HTT KO mice exhibit altered circadian rhythmicity.
- To examine the impact of lifelong serotonin transporter absence on circadian behavior.
- To determine if circadian rhythm abnormalities are a feature of 5-HTT deficiency.
Main Methods:
- Locomotor activity was monitored in wild-type (WT) and 5-HTT KO mice under a 12:12 light-dark cycle.
- Mice were exposed to a light pulse at circadian time 14 and subsequently maintained in constant darkness.
- Analysis focused on circadian period, amplitude, acrophase, and response to photic stimuli.
Main Results:
- No significant differences were observed in circadian period, amplitude, acrophase, or overall activity between WT and 5-HTT KO mice.
- The phase delay response to a light pulse at CT 14 was significantly attenuated in 5-HTT KO mice compared to WT controls.
- These findings indicate normal free-running circadian rhythms but altered light-induced phase shifting.
Conclusions:
- The study demonstrates that the attenuating effect of acute serotonin increases on photic phase shifts is preserved in the absence of the serotonin transporter.
- Lifelong absence of the serotonin transporter does not disrupt core circadian rhythmicity but modulates responses to light.
- These results contribute to understanding the role of serotonin in circadian rhythm regulation and its implications for mood disorders.
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