Treadmill exercise enhances passive avoidance learning in rats: The role of down-regulated serotonin system in the limbic system

Hsiun Ing Chen, Li Chun Lin, Lung Yu, Yu Fan Liu, Yu Min Kuo, A. Min Huang, Jih Ing Chuang, Fong Sen Wu, Pao Chi Liao, Chauying J. Jen

Research output: Contribution to journalArticlepeer-review

54 Citations (Scopus)

Abstract

While serotonin (5-HT) may impair learning and memory, exercise has been reported to improve them. Whether chronic exercise can facilitate fear memory via regulating the serotonin system is unknown. We examined the effects of 4-week treadmill exercise training on levels of 5-HT and its metabolite 5-hydroxyindoleacetic acid (5-HIAA), the protein expression of its receptor 5-HT1A and transporter in the amygdala, hippocampus and prefrontal cortex of male Sprague-Dawley rats. Our results demonstrated that treadmill exercise (1) improved the passive avoidance learning performance; (2) decreased the 5-HT level in the hippocampus; (3) decreased the expression of 5-HT1A receptor in the amygdala without altering the transporter expression. Moreover, pretreatment with 0.1 mg/kg 8-hydroxy-di-n-propylamino tetralin, a selective 5-HT1A receptor agonist, impaired the passive avoidance performance and completely abolished the exercise-enhanced fear memory. Our results suggest that down-regulation of the 5-HT system in the limbic system, i.e., the reduction of the hippocampus 5-HT content and the amygdala 5-HT1A receptor expression, may be involved in the exercise-enhanced fear memory.

Original languageEnglish
Pages (from-to)489-496
Number of pages8
JournalNeurobiology of Learning and Memory
Volume89
Issue number4
DOIs
Publication statusPublished - 2008 May 1

All Science Journal Classification (ASJC) codes

  • Experimental and Cognitive Psychology
  • Cognitive Neuroscience
  • Behavioral Neuroscience

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