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Greenwood et al 2005

Wheel Running Alters Serotonin (5-HT) Transporter, 5-HT 1A , 5-HT 1B , and Alpha 1b -Adrenergic Receptor mRNA in the Rat Raphe Nuclei. Greenwood et al 2005. Depression. Thought to be an overall decrease in serotonin transmission through out the central nervous system.

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Greenwood et al 2005

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  1. Wheel Running Alters Serotonin (5-HT) Transporter, 5-HT1A, 5-HT1B, and Alpha1b-Adrenergic Receptor mRNA in the Rat Raphe Nuclei Greenwood et al 2005

  2. Depression • Thought to be an overall decrease in serotonin transmission through out the central nervous system. • Antidepressants are designed to reverse this process.

  3. Raphe • Serotonin output center of the brain • Thought to be a big source of action for SSRIs • Prevents the reuptake of serotonin increasing neurotransmission • Treats depression

  4. Previous Work • Voluntary wheel running acts as an antidepressent in models • Forced swim • Chronic mild stress • Learned helplessness • 6 weeks wheel running lowers the activity of 5HT neurons in the dorsal raphe nucleus (DRN) during uncontrollable stress • Prevents learned helplessness

  5. M&M • Male Fischer F344 rats individually housed • 12:12hr light/dark cycle • Lights on at 6AM • 1wk acclimatization with locked running wheels • Ad libitum food and water • Unlocked wheels for 3 days, 3 wks, 6wks

  6. What was looked at

  7. Serotonin Transporter (5-HTT)(SERT) Reuptakes 5-HT Pre 5-HTT Pre-synapse 5-HT Post

  8. Serotonin 1A & 1B receptors(5-HT1A & 5-HT1B) • Located on soma, dendrites and axon terminals • Act as auto receptors that inhibit: • Synthesis of 5-HT • Release of 5-HT • Ultra short loop negative feedback

  9. Alpha1B Adrenergic Receptor (α1b ADR) • Coupled Gp-protein / IP3 / Ca++ • Norepinephrine binds • Stimulates Raphe Increases 5-HT output

  10. 5-HTT, 5-HT1A, 5-HT1B, α1b-ADR What technique was used? Problems with this technique • In situ hybridization • Measures mRNA levels • Assumed there is a direct correlation with protein • Translation? • Binding to receptors?

  11. Why were these 4 things looked at? • Estimated that all 5HT neurons in raphe contain these things • All of these things can modulate serotonin transmission in the raphe

  12. Changes in distance and weight

  13. Dorsal Raphe Nucleus (DRN) Median Raphe Nucleus (MR)

  14. ! Increase ! • α1b-ADR • 5-HTT • 5-HT1A • 5-HT1B Decrease !

  15. Seritonin transporter mRNA levels (5-HTT) Relative 5-HTT mRNA levels: integrated optical density

  16. As far as 5HTT is concerned See a decrease in raphe mRNA

  17. Alpha 1B Adrenergic Receptor levels (α1b-ADR) Relative alpha 1b-ADR mRNA levels: Integrated optical density

  18. α1b-ADR (NE receptor) • NE systems are activated by acute exercise • From locus ceruleus • The increased NE levels may down regulate receptors

  19. Seritonin 1B Receptor levels (5-HT1B) Relative 5-HT1B mRNA levels: Integrated optical density

  20. 5-HT1B

  21. 5-HT1B Autoreceptor • Trend of decreasing overall • Exercise and SSRIs decrease • Ventral DRN did show a significant decrease • Selective innervations of certain areas? • Caudate putamen • Cortex • In a separate study, increased 1B makes rats more anxiety prone • suggests an increased capacity to synthesize presynaptic 5-HT1B receptors and could account for diminished serotonin neurotransmission in learned helplessness (Neumaier JF, et al)

  22. Seritonin 1A Receptor levels (5-HT1A) Relative 5-HT1A mRNA levels: Integrated optical density

  23. 5-HT1A autoreceptor • Increased after running • More negative feedback • Opposite of antidepressant treatment • Increased AND decreased levels of 5-HT1A have been seen in suicides or depressed subjects • There’s more to this story

  24. 5-HT1A • Learned helplessness(LH) appears to be dependent on hyperactivation and sensitization of DRN 5-HT neurons. (Takase et al) • LH can also be attenuated by 6wks voluntary wheel running (greenwood) • 5-HT1A increasing after 6 weeks may provide a means of protection from LH • Possibly other depression models as well

  25. Further investigations • Interesting correlation between the time dependent effects of both running and antidepressants • 6 wks but not 3wks of running overcomes learned helplessness in shuttle box (Greenwood)

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