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Alcohol and Stress Hormones

Alcohol and Stress Hormones. Hilary J. Little. Institute of Psychiatry, University of London, United Kingdom. Effects of alcohol. i) Acute effects ii) Long term effects - dependence iii) Interactions with stress hormones. 1. Withdrawal. Acute actions. ?. Tolerance.

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Alcohol and Stress Hormones

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  1. Alcohol and Stress Hormones Hilary J. Little Institute of Psychiatry, University of London, United Kingdom

  2. Effects of alcohol i) Acute effects ii) Long term effects - dependence iii) Interactions with stress hormones 1

  3. Withdrawal Acute actions ? Tolerance Alcohol Dependence Effect on brain normal range Relapse 2 Time Alcohol intake

  4. Acute effects of alcohol Decreases effects of excitatory transmitters, glutamate and aspartate. - particular effect at NMDA receptors - may be relevant to amnesic actions Increases effects pf GABA – in some neurons 5-HT transmission altered (?mood changes?) 3

  5. Acute effects of alcohol Increases release of endogenous opiates Increases mesolimbic dopamine transmission Activates the hypothalamo-pituitary adrenal system (HPA) 4

  6. Drug dependence 1. Withdrawal symptoms 2. Compulsion to take drug 5

  7. The Alcohol Withdrawal Syndrome Anxiety, irritability Tremor, convulsions (can be fatal) Hallucinations, confusion (‘DT’s’) 6

  8. Aims of our experiments i) Neuronal changes during the acute phase of alcohol withdrawal ii) Long term neuronal changes during alcohol abstinence iii) Potential new medication approaches: - glucocorticoid antagonists 7

  9. Clinical evidence for importance of glucocorticoids in alcohol dependence More severe life events (“danger” & “loss”) in years preceding alcohol dependence “High strain” occupations increase risk for alcohol dependence Stressful experiences during abstinence increase likelihood of relapse drinking Stress induces alcohol craving; related to incidence of relapse 8

  10. Cognitive deficits in alcoholics Incidence of cognitive dysfunction in abstinent alcoholics estimated to be 50 to 80% Difficulties in learning new information, retention over long intervals, problems in executive function No current effective treatment 9

  11. Cognitive deficits in alcoholics Neuronal damage after long term alcohol consumption:- frontal association cortex, hippocampus (rodents), thalamus Preclinical and clinical evidence that withdrawal of alcohol after long term consumption plays an important role in memory deficits In high concentrations, glucocorticoid stress hormones (cortisol, corticosterone) cause neurotoxicity and cognitive deficits 10

  12. Stress and drug dependence Stress can alter the effects of many drugs Causes alterations in synaptic plasticity and neuronal survival Such changes include acute, prolonged and delayed effects Stress activates the mesolimbic dopamine system 11

  13. T h e H y p o t h a l a m i c - P i t u i t a r y - A d r e n a l A x i s The HPA axis `C F R P I T U I T A R Y ACTH a d r e n a l s cortisol (or corticosterone) 12

  14. Type I (mineralocorticoid) receptors Corticosterone Type II glucocorticoid receptors Corticosterone in the brain What effects does corticosterone have on the brain during alcohol withdrawal? What are the concentrations of corticosterone in the brain? Why do the concentrations matter? 13

  15. VTA NMDA activation Mesolimbic dopamine system Initial target sites differ, but some common neuronal actions e.g dopamine release Mesolimbic dopamine pathway activated by natural rewards This pathway also activated by stress nucleus accumben DA Alcohol, nicotine, opiates Cocaine, amphetamine 14

  16. ** 4 * 3 2 Firing rate (Hz) 1 0 Effect of corticosterone on firing of ventral tegmental neurones from control animals Basal firing 5 µM NMDA 15 µM NMDA Corticosterone 100 nM aCSF *P < 0.05 **P < 0.01 15

  17. Corticosterone concentrations in rodent brain Measured corticosterone concentrations in brain regions in rodents after chronic alcohol consumption Chronic alcohol treatment and withdrawal Radioimmunoassay after ethanol/DMSO extraction of brain homogenates Identity of corticosterone verified by HPLC and GC-MS 16

  18. ** Blood corticosterone, nM 150 * * 100 ** 50 0 Total Free Regional brain concentrations of corticosterone C57 strain mice Alcohol drinking for 20 weeks Samples 6 days after withdrawal Corticosterone ng/g 300 250 200 150 100 50 0 Brain Hypoth. PFC Hipp. Thal. Cortex Striat. Cereb. stem When alcohol not withdrawn, no changes in brain corticosterone 17

  19. * * 30 * * 20 * * 10 0 Chronic alcohol Regional brain corticosterone concentrations Lister Hooded rats, 8 months drinking, 2 months abstinence Corticosterone ng/g Hypoth Hipp Midbrain PFC Cortex Striatum Plasma concentrations not significantly different Controls 18

  20. Summary: brain corticosterone and alcohol Chronic alcohol consumption increased brain concentrations of the glucocorticoid, corticosterone Plasma levels unchanged Changes seen only after alcohol withdrawal Largest increases in prefrontal cortex and hippocampus 20

  21. Mechanism of brain corticosterone changes after chronic alcohol treatment and withdrawal? Local synthesis of glucocorticoids suggested to occur outside adrenal glands Demonstrated in adipose tissue Occurs via the enzyme 11--hydroxysteroid dehydrogenase (HSD-1) This enzyme is present in brain 20

  22. Relevance of brain glucocorticoid changes? i) Involved in alcohol-induced brain damage? ii) Responsible for cognitive deficits after long term alcohol intake? iii) Alter feedback mechanisms for control of adrenal hormone release? iv) Involved in continued desire to drink alcohol? 21

  23. Current drug treatments for alcohol dependence • Naltrexone • Opiate antagonist • Decreases continuation of drinking once relapse occurs • Acamprosate • Mechanism unknown • Sole action apparently to decrease alcohol intake • Disulphiram (“Antabuse”) • Prevents metabolism of acetaldehyde • this accumulates, producing unpleasant symptoms. • - may help those who really want to stop drinking • Effects: 10 – 20% decrease in relapse drinking 22

  24. ? Effect on brain Withdrawal normal range Relapse ? Time Alcohol withdrawal = window of opportunity? Alcohol intake 23

  25. Alcohol withdrawal = window of opportunity? Multiple withdrawal episodes, more severe withdrawal, higher risk of relapse, greater cognitive deficits Evidence cognitive deficits due to withdrawal rather than to direct effects Acute withdrawal phase offers "window of opportunity" for treatment Drug studied:- i) glucocorticoid Type II receptor antagonist – "mifepristone" 25

  26. Vehicle/alcohol withdrawal Mifepristone /alcohol withdrawal Vehicle/control 4 3 2 1 0 3 4 5 6 7 8 9 Effects of Mifepristone on Alcohol Withdrawal Hyperexcitability in Mice Median response score 3 weeks alcohol via liquid diet Mifepristone/control Injections of vehicle or mifepristone just prior to withdrawal Response to handling measured Time (h) Mifepristone, the Type II glucocorticoid receptor antagonist decreased, but did not prevent, alcohol withdrawal hyperexcitability 25

  27. Object recognition test 26

  28. Vehicle/control Vehicle/alcohol withdrawal Mifepristone /alcohol withdrawal Mifepristone/control 0.5 0.4 0.3 0.2 0.1 0.0 -0.1 Effects of Mifepristone on Memory Deficit in Mice after Alcohol Withdrawal - Object Recognition Test 22 weeks alcohol via drinking fluid * Injections of vehicle or mifepristone just prior to withdrawal Difference in time measured between exploration of novel and familiar objects, 1 week after withdrawal Mifepristone decreased the memory loss seen after withdrawal from chronic alcohol intake 27

  29. Effects of Mifepristone on Neuronal Damage in Organotypic Hippocampal Cultures 20X 5X Propidium iodide fluorescence Mifepristone + corticosterone + alcohol withdrawal Spironolactone + corticosterone + alcohol withdrawal Alcohol withdrawal Corticosterone + alcohol withdrawal Control • Corticosterone greatly increased the neuronal damage caused by • withdrawal of alcohol. • Mifepristone, but not spironolactone prevented this effect of • corticosterone 28 Collaboration with University of Kentucky

  30. Alcohol preference ratio 0.6 0.5 0.4 0.3 0.2 0.1 0.0 4 6 8 10 12 14 16 18 20 0 2 Effects of Type II glucocorticoid receptor antagonist mifepristone (RU38486) on alcohol preference in mice Low alcohol preferring mice Saline injections Mifepristone injections Choice 8% alcohol v tap water Once daily injections of isotonic saline or Type II receptor antagonist === === === *** *** *** Day Slowly developing increase in alcohol preference and consumption Effect prevented by mifepristone 29

  31. Clinical Trial of Mifepristone in Alcoholics Participants - alcoholics entering the Alcohol Unit for detoxification Treatment - mifepristone or placebo for two weeks from cessation of drinking Testing – depression ratings and cognitive test battery (CANTAB) during weeks 3 and 4 Follow-up – 3,6 and 12 months to record relapse drinking 30

  32. Mifepristone as a Potential Treatment? • Glucocorticoid Type II receptor antagonist e.g. mifepristone • Reduced withdrawal severity • Reduced memory loss • Prevented neurotoxicity in vitro • Prevent stress-induced increases in alcohol drinking • ?effective in alcoholics - study in progress 32

  33. Future treatments for drug dependence? 1980s Little research on drug dependence was supported by government funding 1990s Drug dependence becomes a special target area for research 2000s Possibility accepted of medication treatment for alcohol dependence Next? ? Development of effective treatments to prevent dependence and memory loss?

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