Visceral Pain-Related Anxiety: Role of Glucocorticoids Brent Myers, Ph.D. Department of Psychiatry University of Cincinnati Center for Neuroscience University of Oklahoma Health Sciences Center
Irritable Bowel Syndrome A gastrointestinal disorder where altered visceral perception leads to chronic abdominal pain that is exacerbated during periods of stress and anxiety Behavioral Anxiety Physiological Abdominal Pain Irritable Bowel Syndrome
(Adapted from Whitehead et al. 198, Dunphy et al. 23) Pain Hypersensitivity in IBS Visceral Somatic 6 5 IBS Controls 7 6 IBS Controls Foot Percent Reporting Pain 4 3 2 1 VAS Intensity 5 4 3 2 1 Hand Foot Hand 2 4 6 8 1 12 14 16 18 45 47 Distension Volume (ml) Stimulus Level ( o C)
9 12 15 18 21 24 3 6 9 HPA Activity in IBS Patients Mean Cortisol (ug/dl) 14 12 1 8 6 4 2 Diurnal Rhythm IBS Controls Hourly Cortisol Secretion (Adapted from Chang et al. 28, Dinan et al. 26) ACTH (ng/l) Cortisol (nmol/l) 3 2 1 8 7 6 5 4 3 2 1 CRF Challenge IBS Controls -15 15 3 45 6 9 12 Time (min) IBS Controls -15 15 3 45 6 9 12 Time (min)
(Herman et al. 23, Naliboff et al. 23, Neugebauer et al. 26) The Amygdala in IBS IBS patients display greater amygdala activity than controls The amygdala is an important regulator of pain affect HPA and ANS stress responses are facilitated by the amygdala
(Myers and Greenwood-Van Meerveld, Am J Phys 21; Shepard et al. 23) Amygdala Implant Model CORT (ng/ml) 2 15 1 5 CHOL CORT 7 AM 7 PM A B CORT (ng/ml) 4 3 2 CHOL CORT 1 1 mm m c b 1 mm -15 15 45 9 Time (min)
Time in Open Arms (% of Cholesterol) (Greenwood-Van Meerveld et al. 21) Amygdaloid CORT Induces Anxiety-Like Behavior 1 75 5 25 CHOL CORT
Hypothesis #1 Amygdaloid CORT induces viscerosomatic hypersensitivity as well as anxiety-like behavior
(Greenwood-Van Meerveld et al. 23) Visceral Sensitivity Assessment The level of visceral pain is determined by a visceromotor behavioral response (VMR) to colorectal distension (CRD) This nociceptive or pseudoaffective response is displayed as contractions of the external abdominal oblique muscle Instrumentation CRD 1 min Recovery 3 min
Experimental Design Acclimate to Animal Facility Stereotaxic Implant Anxiety Assessment 7 Days 5 Days 2 Days Visceral Sensitivity Assessment mmhg 2 mmhg 4 mmhg 6 mmhg 1 min 1 min
Time in Open Arms (%) Effect of CORT in the Amygdala 9 8 7 6 5 4 3 2 1 Cholesterol 15 3 CORT (mg) Rats with 3 mg of CORT exhibited responses that were indicative of anxiety while a lower concentration of CORT was ineffective p<.1 vs. cholesterol; p<.5 vs. 15 mg (Myers and Greenwood-Van Meerveld, Am J Physiol 27)
Number of Abdominal Contractions/1 min p<.5,p<.1,p<.1 vs. cholesterol (Myers and Greenwood-Van Meerveld, Am J Physiol 27) Effect of CORT in the Amygdala 4 35 3 Cholesterol CORT (15 mg) CORT (3 mg) 25 2 15 1 5 2 4 6 Colonic Distension Pressure (mmhg) Rats implanted with CORT displayed visceral hypersensitivity in response to colorectal distension (CRD)
Are the Effects of CORT Specific to the Amygdala? Other structures were targeted to determine the amygdala specificity of CORT-induced effects on anxiety and visceral sensitivity Hippocampus Caudate Putamen
Time in Open Arms (%) p<.5,p<.1,p<.1 (Myers and Greenwood-Van Meerveld, Am J Physiol 27) Number of Abdominal Contractions/1 min Are the Effects of CORT Specific to the Amygdala? Anxiety Visceral Sensitivity 9 8 7 6 5 4 3 2 1 CA3 CPu CeA 4 35 3 25 2 15 1 5 CeA CA3 CPu 2 4 6 Distension Pressure (mmhg) The effects of CORT on anxiety and visceral sensitivity were specific to the amygdala and not due to diffusion into adjacent brain regions
Are the Effects of CORT Specific to Visceral Pain? Acclimate to Animal Facility Stereotaxic Implant Von Frey 7 Days 5 Days 2 Days Tail Flick Von Frey Tail Flick
Time (s) Force (g) Effect of CORT on Somatic Pain Tail Flick Von Frey 1 9 8 7 7 6 5 7 6 5 6 5 4 4 3 4 3 3 2 1 Cholesterol CORT 2 1 Cholesterol CORT 2 1 Hippocampus CeA CORT induced somatic allodynia suggesting that modulation of the amygdala with CORT results in a generalized decrease in nociceptive thresholds via descending neuronal pathways p<.1 vs. cholesterol or hippocampus (Myers et al., Behav Brain Res 27)
Hypothesis #2 The effects of Amygdaloid CORT on viscerosomatic hypersensitivity and anxiety-like behavior are persistent
Experimental Design Acclimate to Animal Facility Stereotaxic Implant Anxiety & Somatic Assessment Visceral Sensitivity Assessment 7 Days 5, 12, or 26 Days 2 Days 6 Experimental Groups 7 Day CORT 7 Day Chol 14 Day CORT 14 Day Chol 28 Day CORT 28 Day Chol
Time in Open Arms (%) Persistent Effect of CORT on Anxiety-Like Behavior 9 8 Chol CORT 7 6 5 4 3 2 1 7 Day 14 Day 28 Day CORT induced a long-term increase in anxiety-like behavior p<.5, p<.1, p<.1 compared to chol (Myers and Greenwood-Van Meerveld, submitted)
Force Eliciting Withdrawal (g) Persistent Effect of CORT on Somatic Pain 7 6 5 4 Chol CORT 3 2 1 7 Day 14 Day 28 Day Amygdaloid CORT led to a sustained decrease in somatic thresholds p<.5 compared to chol (Myers and Greenwood-Van Meerveld, submitted)
Abdominal Contractions/1 min Persistent Effect of CORT on Visceral Sensitivity 4 35 3 25 2 15 1 5 7 Day 35 3 25 2 15 1 5 14 Day 28 Day 4 4 2 4 6 2 4 6 2 4 6 35 3 25 2 15 1 5 Colonic Distension Pressure (mmhg) CHOL CORT Elevated amygdaloid CORT induced long-term visceral hyperalgesia p<.1 p<.1 compared to chol (Myers and Greenwood-Van Meerveld, submitted)
Hypothesis #3 Amygdaloid CORT regulates anxiety and visceral hypersensitivity through specific steroid receptormediated mechanisms
Experimental Design Acclimate to Animal Facility Stereotaxic Implant Anxiety Assessment 7 Days 5 Days 2 Days Visceral Sensitivity Assessment 7 Groups CORT (3 mg) CORT + GR Antagonist (Mifepristone: 3, 15, 3 mg) CORT + MR Antagonist (Spironolactone: 3, 15, 3 mg)
Number of Abdominal Contractions/1 min p<.5,p<.1,p<.1 vs. CORT (Myers and Greenwood-Van Meerveld, Am J Physiol 27) Time in Open Arms (%) What are the Effects of Combining CORT with a GR Antagonist? Visceral Sensitivity Anxiety 4 35 3 25 2 15 1 5 CORT (3 mg) Mifepristone (3 mg) Mifepristone (15 mg) Mifepristone (3 mg) 2 4 6 Colonic Distension Pressure (mmhg) 9 8 7 6 5 4 3 2 1 CORT Mife (3 mg) In rats with CORT implants combined with a GR antagonist there was a significant inhibition of visceral hypersensitivity and anxiety
Number of Abdominal Contractions/1 min p<.5,p<.1,p<.1 vs. CORT (Myers and Greenwood-Van Meerveld, Am J Physiol 27) Time in Open Arms (%) What are the Effects of Combining CORT with a MR Antagonist? Visceral Sensitivity Anxiety 4 35 3 25 2 15 1 5 CORT (3 mg) Spironolactone (3 mg) Spironolactone (15 mg) Spironolactone (3 mg) 2 4 6 Colonic Distension Pressure (mmhg) 9 8 7 6 5 4 3 2 1 CORT Spiro (15 mg) Animals that received micropellets of spironolactone combined with CORT showed a reduction in visceral sensitivity and anxiety
Experimental Design Acclimate to Animal Facility Stereotaxic Implant Somatic Sensitivity & Anxiety 7 Days 5 Days 2 Days Visceral Sensitivity Assessment 7 Groups Cholesterol (Control: 3 mg) GR Agonist (Dexamethasone: 3, 15, 3 mg) MR Agonist (Aldosterone: 3, 15, 3 mg)
Time in Open Arms (%) p<.5,p<.1 vs. cholesterol (Myers and Greenwood-Van Meerveld, Am J Phys 21) Does GR or MR Activation Affect Anxiety? 9 9 8 7 8 7 6 5 4 6 5 4 3 2 3 2 1 1 Chol 3 15 3 Dexamethasone (mg) Chol 3 15 3 Aldosterone (mg) Both GR and MR activation induced anxiety-like behavior
Abdominal Contractions/1 min What are the GR and MR-Mediated Effects on Visceral Pain? 4 35 3 25 2 15 Chol Dex (3 mg) Dex (15 mg) Dex (3 mg) 4 35 3 25 2 15 Chol Aldo (3 mg) Aldo (15 mg) Aldo (3 mg) 1 1 5 5 2 4 6 2 4 6 Distension Pressure (mmhg) Distension Pressure (mmhg) MR was involved in the allodynic response to CRD while both GR and MR were involved in visceral hyperalgesia p<.5,p<.1,p<.1 vs. cholesterol (Myers and Greenwood-Van Meerveld, Am J Phys 21)
Force Eliciting Withdrawal (g) p<.1 vs. cholesterol (Myers and Greenwood-Van Meerveld, Am J Phys 21) Does GR or MR Activation Alter Somatic Pain Thresholds? 7 7 6 6 5 4 5 4 3 3 2 2 1 1 Chol 3 15 3 Dexamethasone (mg) Chol 3 15 3 Aldosterone (mg) GR but not MR altered somatic pain thresholds
Hypothesis #4 The involvement of amygdaloid GR and MR in stress-induced visceral hypersensitivity is pathophysiologically relevant
Experimental Design: Repeated WAS Day 1 Day 7 Stereotaxic Implant WAS or Sham (1 hr) WAS or Sham (1 hr) VMR 5 Days 1 h or 24 h Home Cage Control: Cholesterol implant and VMR on Day 7
Stress-Induced Autonomic Activity 6 WAS 5 Sham Stress Fecal Pellet Output 4 3 2 1 1 2 3 4 5 6 7 Day Repeated stress increased colonic motor activity p<.5, p<.1, p<.1 vs. Sham; p<.5, p<.1 compared to Sham Day 1 (Myers and Greenwood-Van Meerveld, Neurogastroenterol Motil 29)
Abdominal Contractions Visceral Sensitivity after Repeated WAS 1 h Post-Stress 24 h Post-Stress 3 25 2 15 WAS Sham Stress Home Cage 3 25 2 15 WAS Sham Stress Home Cage 1 1 5 5 2 4 6 2 4 6 Distension Pressure (mmhg) Distension Pressure (mmhg) Repeated behavioral stress increased visceral sensitivity p<.1 vs. Sham; p<.1, p<.1 vs. Home Cage (Myers and Greenwood-Van Meerveld, Neurogastroenterol Motil 29)
Abdominal Contractions Visceral Sensitivity after Repeated WAS 1 h Post-Stress 24 h Post-Stress 3 25 2 15 WAS WAS + Mifepristone WAS + Spironolactone 3 25 2 15 WAS WAS + Mifepristone WAS + Spironolactone 1 1 5 5 2 4 6 2 4 6 Distension Pressure (mmhg) Distension Pressure (mmhg) GR and MR antagonists blocked the immediate and sustained effects of stress on visceral sensitivity p<.5, p<.1, p<.1 vs. Mifepristone; p<.1, p<.1 vs. Spironolactone (Myers and Greenwood-Van Meerveld, Neurogastroenterol Motil 29)
Stress-Induced Autonomic Activity Fecal Pellet Output 6 5 4 3 2 WAS WAS + Mifepristone WAS + Spironolactone 1 1 2 3 4 5 6 7 Day The effects of stress on colonic motor activity were not inhibited by GR or MR antagonists p<.1 vs. Mifepristone Day 1; p<.1, p<.1 compared to Spironolactone Day 1 (Myers and Greenwood-Van Meerveld, Neurogastroenterol Motil 29)
Summary Elevated CORT in the amygdala leads to long-term changes in anxiety-like behavior and pain sensitivity CORT-induced anxiety-like behavior and pain hypersensitivity are mediated by specific GR and MR mechanisms GR and MR in the amygdala are essential for repeated psychological stress-induced visceral hypersensitivity
Conclusion Corticosteroids acting through specific receptors at the level of the amygdala may contribute to the relationship between anxiety disorders and chronic pain conditions such as IBS
Acknowledgements Dr. Greenwood-Van Meerveld s Laboratory The Oklahoma Center for Neuroscience Department of Veterans Affairs American Society of Pharmacology and Experimental Therapeutics