1. The effects of brain serotonin deficiency on the behavioral and neurogenesis-promoting effects of voluntary exercise in tryptophan hydroxylase 2 (R439H) knock-in mice.
- Author
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Warner AK, Iskander L, Allen K, Quatela I, Borrelli H, and Sachs BD
- Subjects
- Animals, Male, Female, Mice, Hippocampus metabolism, Hippocampus drug effects, Mice, Transgenic, Brain metabolism, Brain drug effects, Mice, Inbred C57BL, Gene Knock-In Techniques, Behavior, Animal drug effects, Behavior, Animal physiology, Tryptophan Hydroxylase metabolism, Tryptophan Hydroxylase genetics, Neurogenesis physiology, Neurogenesis drug effects, Serotonin metabolism, Physical Conditioning, Animal physiology
- Abstract
Exercise is known to reduce depression and anxiety symptoms. Although the cellular and molecular mechanisms underlying this effect remain unknown, exercise-induced increases in neurotransmitter release and hippocampal neurogenesis have been hypothesized to play key roles. One neurotransmitter that has been implicated in both antidepressant-like effects and the regulation of hippocampal neurogenesis is serotonin (5-HT). Complete loss of function of the brain 5-HT synthesis enzyme (tryptophan hydroxylase 2, Tph2) has been reported to prevent exercise-induced increases in neurogenesis and to block a subset of antidepressant-like responses to selective serotonin reuptake inhibitors (SSRIs), but whether partial loss of Tph2 function blocks the behavioral and neurogenic effects of exercise has not been established. This study used four tests that are predictive of antidepressant efficacy to determine the impact of 5-HT deficiency on responses to exercise in male and female mice. Our results demonstrate that low 5-HT impairs the behavioral effects of exercise in females in the forced swim and novelty-suppressed feeding tests. However, genetic reductions in 5-HT synthesis did not significantly impact exercise-induced alterations in cellular proliferation or immature neuron production in the hippocampus in either sex. These findings highlight the importance of brain 5-HT in mediating behavioral responses to exercise and suggest that individual differences in brain 5-HT synthesis could influence sensitivity to the mental health benefits of exercise. Furthermore, the observed disconnect between neurogenic and behavioral responses to exercise suggests that increased neurogenesis is unlikely to be the primary driver of the behavioral effects of exercise observed here., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)
- Published
- 2024
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