Testosterone, Aggression, and Impulsivity in Rats

1. Testosterone, Aggression, and Impulsivity in Rats Erik Manke March 7, 2014

2. Steroids vs. Water Bottle http://www.youtube.com/watch?v=Yn5iIF95Qho Arnold Visits Hans and Franz http://screen.yahoo.com/pumping-hans-franz-arnold-schwarzenegger-000000067.html

3. Defining Impulsivity • Kerman et al. 2011 • Marked decreases in behavioral/emotional control, lack of perception, brash decision making • Batrinos 2012 • Lack of restraint, disuse of PFC, absence of inhibition, and emotionality • Wood et al. 2013 • Immediate disregard in decision making, impatience, short term decisions, and reactive aggression

4. Testosterone and Impulsivity • Kerman et al. 2011 • bHR rats (impulsive phenotype)  Increased Aggression  Increased Testosterone x2 and Corticosterone • Batrinos 2012 • Testosterone  Activated Amygdala  Increased Emotional Activity  Decreased Pre-frontal Inhibition of Motor Control • Wood et al. 2013 • Testosterone Increased Aggression but Reduced CPu TH  Decrease Impulsivity

5. Questions/Themes/Hypotheses • Kerman et al. 2011 • Hypothesis- bHR rats = higher aggression, altered 5-HTergic cells in brainstem • Compare/contrast bHR/bLR rats’ behaviors, neurochemistry, and hormone levels • Differential expression of Tph2 and Sert versus c-fos in rats depending on brain region and phenotype

6. Questions/Themes/Hypotheses (cont.) • Batrinos 2012 • Relationship of Testosterone and Cortisol • Testosterone  Activated Amygdala  Increased Emotional Activity  Decreased Pre-frontal Inhibition of Motor Control (increased impulsivity) • Cortisol  Increased Pre-frontal cortex control (decreased impulsivity) • Seratonin  Inhibits motor impulsivity • Testosterone, cortisol, and serotonin form a triad

7. Questions/Themes/Hypotheses (cont.) • Wood et al. 2013 • How do AAS affect impulsivity? Through DA? • Acb, CPu, PFC, and VTA/SN • AAS  Aggressive Behavior  DA from Hypothalamus  Increased aggression and Impulsivity

8. Kerman et al. 2011 High/Low Responder Rats

9. bHR and bLR Rats • Selectively-bred high and low responder rats • Many generations bred for distinct behaviors • bHR rats = Phenotypically impulsive • “…heightened novelty-induced exploration, impulsivity, and increased sensitivity to drugs of abuse.” • bLR rats = Phenotypically non-impulsive • “…exaggerated depressive and anxiety-like behaviors.”

10. Serotonin • Key role in aggressive responses • Influx upon resident/intruder experiments • Measured by Tph2 (synthesis) and Sert (reuptake) gene expression • Expression inhibits c-fos expression • Expect high Tph2 and Sert in bHR rats • Expect high c-fos in bLR rats

11. Figure 1: Behavioral differences between bHR and bLR rats

12. Figure 2: Relative Testosterone/Corticosterone Levels in bHR versus bLR rats before and after intrusion

13. Figure 3: Serotonergic cell groups in rat brainstem sections caudal (A) to rostral (T)

14. Figure 4: Tph2 (top) and Sert (bottom) expression differences between bHR rats (left) and bLR rats (right)- Significance in B9 cell group and pontomesencephalic reticular formation

15. Figure 5: Greater Tph2 expression in bHR rats compared to bLR rats

16. Figure 6: Greater Sert expression in bHR rats compared to bLR rats

17. Figure 7: Sert expression (red) and c-fos expresssion (green) and overlay in bLR (left) versus bHR (right)

18. Figure 8: c-fos expression greater in bLR rats compared to bHR rats in certain regions

19. Batrinos 2012 Testosterone and (He?)Man I Said Hey!

20. The triad • Testosterone vs. Cortisol/Serotonin • PET and fMRI allow locality and interactions to be determined • Ratios determine aggressiveness, anti-social behavior, anger, and possibly impulsiveness

21. Testosterone • Associated with aggression/anti-social behavior • Violent vs. non-violent prisoners • Testosterone dosing • CAG repeats in human androgen receptor promoter • Testosterone  Amygdala  Reduced pre-frontal cortex inhibition (higher impulsivity) • Local brain testosterone > effect than circulatory

22. Cortisol • Antagonist to testosterone • Inhibits GnRH • Linked to submissive behavior • Cortisol  Testosterone  Decreased Impulsivity • Testosterone inhibits CRH • Testosterone/Cortisol ratio may predict impulsivity

23. Serotonin • Counteracts testosterone • Regulates impulsivity and aggressiveness • Both activating and inhibitory neurons in pre-frontal and subcortical areas • High pre-frontal serotonin = low impulsivity

25. Wood et al. 2013 ‘Roid rage in rats?

26. Nose Poke Test • Male rats trained for nose poke response to light for potential fight • Resident/Intruder Model (5 min) • FI10 Schedule • Measure operant response • Measure acts of aggression

27. Figure 1: Operant Responses -Significant differences= * -No difference between testo/vehicle for operant responses/rate -Testo rats fought more/earlier -Vehicle rats in contact more often/longer

28. Delayed-Discounting Procedure • 2 retractable levers with control on sides • Light stimulus • 70 s trial with 10 s response window • Initially equal rewards 1 forced trial • Large reward delay increased by 15 s increments • Impulsive = immediate reward (1 pellet) • Not Impulsive = delayed reward (4 pellets)

29. Figure 2: Delay-Discounting Impulsivity -No significant differences between Vehicle/Testo Rats -Tested body weight (A) -Food per session (B) -Food per day (C) -Unreinforced Trials per session (D)

30. Figure 3: Large Reward Preference -Small/Immediate reward= impulsive preference -Large/Delayed reward=non-impulsive preference -Only significant at 45 second delay -Trend -Q: Why are testosterone rats less impulsive? A: Look at Immunoblots

31. Western Immunoblot • 20 week old rat brains • Measure target protein (TH) levels • PFC, Acb, CPu, VTA/SN • Primary Antibodies for TH and beta-tubulin • Secondary Antibodies for fluorescence • Ratio of TH to beta tubulin measured

32. Tyrosine Pathway TH Rate limiting enzyme

33. Figure 4: Western Immunoblot (Top) and TH Levels (Bottom) -Top-Caudate/Putamen TH and beta tubulin protein expression -Bottom- Testo/Vehicle TH levels only significantly differ in the Caudate/Putamen -Q: What does this mean? A: CPu causes disinhibition of thalamus increasing impulsivity

35. Reactive vs Proactive Aggression Chris Benoit 2007 Double Murder Suicide

36. Answering the Focal Questions • Kerman et al. 2011 • Impulsive phenotype (bHR) • Increase in Aggression  increase 5-HT • Two fold increase in testosterone and corticosterone • Increased Tph2 and Sert expression • Decreased c-fos expression • bHR rats exhibit elevated gene expression levels causing elevated aggression (possibly impulsivity?)

37. Answering the Focal Questions (cont.) • Batrinos et al. 2012 • Testosterone/cortisol ratio and serotonin levels form impulsiveness regulatory triad • Primary interaction = amygdala and pre-frontal cortex • Aggression and Impulsiveness closely tied

38. Answering the Focal Questions (cont.) • Wood et al. 2013 • TH levels in Acb, VTA/SN, and PFC = same in Immunoblot study for vehicle/testo • CPu TH lower and delayed reward higher in testo reflected lower impulsivity • Testosterone does not  Greater impulsivity • Testosterone may  Less impulsivity

39. Final Thoughts/Conclusions • Three modes of thinking regarding testosterone and impulsivity: 1. Phenotypic impulsivity  higher aggression  higher testosterone 2. Increased testosterone  decrease pre-frontal cortex motor control  increase impulsivity 3. Testosterone Increased Aggression but Reduced CPu TH  Decrease Impulsivity

40. Works Cited Batrinos, M. L. 2012. Testosterone and aggressive behavior in man. International Journal of Endocrinology & Metabolism 10(3): 563-568. Kerman, I. A., Clinton, S. M., Bedrosian, T. A., Abraham, A. D., Rosenthal, D. T., Akil, H., & Watson, S. J. 2011. High novelty-seeking predicts aggression and gene expression differences within defined serotonergic cell groups. Brain Research 1419: 34-45. Montoya, E. R., Terberg, D., Bos, P. A., & Van Honk, J. 2011. Testosterone, cortisol, and serotonin as key regulators of social aggression: A review and theoretical perspective. Motivation and Emotion 36: 65-73. Wood, R. I., Armstrong, A., Fridkin, V., Shah, V., Najafi, A., & Jakowec, M. 2013. ‘Roid rage in rats? Testosterone effects on aggressive motivation, impulsivity and tyrosine hydroxylase. Physiology & Behavior 110- 111: 6-12.