The Effects of Ethanol and Ethanol Metabolites on Locomotor Activation and Ataxia: Focus on the Substantia Nigra pars Reti...
Biphasic Effects <ul><li>Ethanol is typically classified as a sedative hypnotic </li></ul><ul><li>Many studies have shown ...
Biphasic Effect in Mice and Humans <ul><li>Biphasic effects first shown in mice  Read et al. 1960 </li></ul><ul><li>Many s...
Biphasic Effects in Rats <ul><li>Only sedative effects have been seen in rats via peripheral administration (i.p. or oral)...
Effects of Ethanol, Acetaldehyde, and Acetate on Locomotor Activity in Rats: Open Field
<ul><li>In the proposed set of experiments the focus will be on the activating effects low doses ethanol </li></ul>
Ethanol infused into lateral ventricles: locomotor activity  First 10 minutes stabilimeter
Ethanol Metabolism
Peripheral Metabolism Ethanol Acetaldehyde Acetate ADH, CYP 450, CAT ALDH
Brain Metabolism Ethanol Acetaldehyde Acetate CAT ALDH
Are the metabolites active?
Effects of Ethanol, Acetaldehyde, and Acetate on Locomotor Activity in Rats: Open Field
0 20 40 60 80 100 120 ACETALDEHYDE DOSE (  mol) ** ** * MOTOR ACTIVITY (counts in 10 minutes ) ETHANOL DOSE (  mol ) Eth...
Working Hypotheses <ul><li>Acetaldehyde increases behavior </li></ul><ul><ul><li>Increases open field and stabilimeter act...
FR5 high doses
What are the brain areas that mediate the activating effects of ethanol and acetaldehyde?
<ul><li>VTA? </li></ul><ul><li>NAcc? </li></ul><ul><li>CPU? </li></ul><ul><li>SNr? </li></ul>
SNr and Motor Behavior <ul><li>Muscle rigidity  Crocker 1997 </li></ul><ul><li>Lever pressing  Correa et al. submitted, Tr...
SNc STRIATUM SNr DA GABA
SNr STRIATUM STN Superior Colliculus Reticular Formation Brainstem Motor Motor Thalamus
SNr, GABA, and Motor Behavior <ul><li>GABA agonists and antagonists have their most potent effect on locomotion when infus...
Ethanol and GABA <ul><li>Modulation of GABA transmission </li></ul><ul><li>Facilitation of GABA A  receptor function </li>...
Why SNr? <ul><li>GABA manipulations in SNr effect locomotor behavior </li></ul><ul><li>Ethanol works through the GABA rece...
Focus on the SNr SNc SNr
List of Experiments Acetate Ataxia Experiment 9 Acetaldehyde Ataxia Experiment 8 Ethanol Ataxia Experiment 7 Acetaldehyde,...
List of Experiments Acetate Ataxia Experiment 9 Acetaldehyde Ataxia Experiment 8 Ethanol Ataxia Experiment 7 Acetaldehyde,...
 
 
Preliminary data
Preliminary data
Preliminary data
List of Experiments Acetate Ataxia Experiment 9 Acetaldehyde Ataxia Experiment 8 Ethanol Ataxia Experiment 7 Acetaldehyde,...
 
Sedation Scale <ul><li>4 – awake, active </li></ul><ul><ul><li>Engaged in locomotion, rearing, or head movements </li></ul...
Hypotheses <ul><li>Ethanol infused into the SNr will have an activating effect on locomotor behavior at low doses </li></u...
Hypotheses (continued) <ul><li>The behavioral activating effect of ethanol infused in the SNr can be blocked with peripher...
Hypotheses (continued) <ul><li>Low doses of ethanol and acetaldehyde infused into the SNr will not produce ataxia </li></u...
<ul><li>The results of the proposed experiments will further elucidate the brain mechanisms and biochemical pathways throu...
 
<ul><li>Effects on neurotransmission </li></ul>GABA.  Like benzodiazepines, barbiturates and anesthetics, acute ethanol en...
DA.  Acute and Chronic alcohol administration induces dopamine release in the N. Accumbens.  5-HT.  Acute ethanol induces ...
Endogenous Opioids . Acute alcohol increases endorphin and enkephalin expression and release. Chronic alcohol produces the...
Evidence of central ethanol metabolism by Catalase. <ul><li>Catalase is widespread in brain, and also is localized in seve...
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Dissertation Proposal

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Dissertation Proposal

  1. 1. The Effects of Ethanol and Ethanol Metabolites on Locomotor Activation and Ataxia: Focus on the Substantia Nigra pars Reticulata Maria Arizzi, M.A. Dissertation Proposal
  2. 2. Biphasic Effects <ul><li>Ethanol is typically classified as a sedative hypnotic </li></ul><ul><li>Many studies have shown activating as well as depressant effects after ethanol administration </li></ul>
  3. 3. Biphasic Effect in Mice and Humans <ul><li>Biphasic effects first shown in mice Read et al. 1960 </li></ul><ul><li>Many studies since have confirmed this finding </li></ul><ul><li>Recent research in humans has also shown biphasic effects of ethanol </li></ul><ul><ul><li>Self-report – BAES Earleywine and colleagues </li></ul></ul><ul><ul><li>Biological measurements Davidson et al. 1997, 2002, Grassi et al. 1989, Higgins et al. 1993, Inder et al. 1995, Rush et al. 1993 </li></ul></ul>
  4. 4. Biphasic Effects in Rats <ul><li>Only sedative effects have been seen in rats via peripheral administration (i.p. or oral) of ethanol Bass et al. 1979, Duncan et al. 2000, George et al. 1990, Gingras et al. 1996, Little et al. 1996, Moore et al. 1993, Petry et al. 1998, Pohorecky 1977 </li></ul><ul><li>Recent work using intraventricular administration has shown a biphasic effect of ethanol in rats </li></ul>
  5. 5. Effects of Ethanol, Acetaldehyde, and Acetate on Locomotor Activity in Rats: Open Field
  6. 6. <ul><li>In the proposed set of experiments the focus will be on the activating effects low doses ethanol </li></ul>
  7. 7. Ethanol infused into lateral ventricles: locomotor activity First 10 minutes stabilimeter
  8. 8. Ethanol Metabolism
  9. 9. Peripheral Metabolism Ethanol Acetaldehyde Acetate ADH, CYP 450, CAT ALDH
  10. 10. Brain Metabolism Ethanol Acetaldehyde Acetate CAT ALDH
  11. 11. Are the metabolites active?
  12. 12. Effects of Ethanol, Acetaldehyde, and Acetate on Locomotor Activity in Rats: Open Field
  13. 13. 0 20 40 60 80 100 120 ACETALDEHYDE DOSE (  mol) ** ** * MOTOR ACTIVITY (counts in 10 minutes ) ETHANOL DOSE (  mol ) Ethanol and Acetaldehyde infused in to the lateral ventricles: First 10 minutes, stabilimeter 0 0.7 1.4 2.8
  14. 14. Working Hypotheses <ul><li>Acetaldehyde increases behavior </li></ul><ul><ul><li>Increases open field and stabilimeter activity </li></ul></ul><ul><ul><li>Increases operant behavior on low rate schedules </li></ul></ul><ul><li>Acetate decreases behavior </li></ul><ul><ul><li>Decreases open field activity </li></ul></ul><ul><ul><li>Decreased operant on high rate schedules </li></ul></ul>
  15. 15. FR5 high doses
  16. 16. What are the brain areas that mediate the activating effects of ethanol and acetaldehyde?
  17. 17. <ul><li>VTA? </li></ul><ul><li>NAcc? </li></ul><ul><li>CPU? </li></ul><ul><li>SNr? </li></ul>
  18. 18. SNr and Motor Behavior <ul><li>Muscle rigidity Crocker 1997 </li></ul><ul><li>Lever pressing Correa et al. submitted, Trevitt et al. 2001 </li></ul><ul><li>Tremor Finn et al. 1997, Mayorga et al. 1999 </li></ul><ul><li>Catalepsy Scheel-Krueger et al. 1977 </li></ul><ul><li>Circling Scheel-Krueger et al. 1977 </li></ul><ul><li>Locomotion Abraini et al. 1999, Scheel-Krueger et al. 1977, 1981, Trevitt et al. 2002 </li></ul>
  19. 19. SNc STRIATUM SNr DA GABA
  20. 20. SNr STRIATUM STN Superior Colliculus Reticular Formation Brainstem Motor Motor Thalamus
  21. 21. SNr, GABA, and Motor Behavior <ul><li>GABA agonists and antagonists have their most potent effect on locomotion when infused into the SNr </li></ul><ul><li>Dopaminergic stimulation in the SNr increases locomotion and increases GABA release in the SNr </li></ul><ul><li>Locomotor effect attenuated by infusion of GABA A antagonist </li></ul>Trevitt et al. 2002
  22. 22. Ethanol and GABA <ul><li>Modulation of GABA transmission </li></ul><ul><li>Facilitation of GABA A receptor function </li></ul>
  23. 23. Why SNr? <ul><li>GABA manipulations in SNr effect locomotor behavior </li></ul><ul><li>Ethanol works through the GABA receptor </li></ul><ul><li>SNr is a part of the basal ganglia circuitry important for the modulation of locomotion and motor function </li></ul><ul><li>SN has relatively high density of catalase and is therefore a possible place for acetaldehyde action </li></ul>
  24. 24. Focus on the SNr SNc SNr
  25. 25. List of Experiments Acetate Ataxia Experiment 9 Acetaldehyde Ataxia Experiment 8 Ethanol Ataxia Experiment 7 Acetaldehyde, sodium azide Locomotor Activity Experiment 6 Ethanol, sodium azide Locomotor Activity Experiment 5 Acetate Locomotor Activity Experiment 4 Acetaldehyde Locomotor Activity Experiment 3 Ethanol, dorsal site Locomotor Activity Experiment 2 Ethanol Locomotor Activity Experiment 1 Drug Task Experiment
  26. 26. List of Experiments Acetate Ataxia Experiment 9 Acetaldehyde Ataxia Experiment 8 Ethanol Ataxia Experiment 7 Acetaldehyde, sodium azide Locomotor Activity Experiment 6 Ethanol, sodium azide Locomotor Activity Experiment 5 Acetate Locomotor Activity Experiment 4 Acetaldehyde Locomotor Activity Experiment 3 Ethanol, dorsal site Locomotor Activity Experiment 2 Ethanol Locomotor Activity Experiment 1 Drug Task Experiment
  27. 29. Preliminary data
  28. 30. Preliminary data
  29. 31. Preliminary data
  30. 32. List of Experiments Acetate Ataxia Experiment 9 Acetaldehyde Ataxia Experiment 8 Ethanol Ataxia Experiment 7 Acetaldehyde, sodium azide Locomotor Activity Experiment 6 Ethanol, sodium azide Locomotor Activity Experiment 5 Acetate Locomotor Activity Experiment 4 Acetaldehyde Locomotor Activity Experiment 3 Ethanol, dorsal site Locomotor Activity Experiment 2 Ethanol Locomotor Activity Experiment 1 Drug Task Experiment
  31. 34. Sedation Scale <ul><li>4 – awake, active </li></ul><ul><ul><li>Engaged in locomotion, rearing, or head movements </li></ul></ul><ul><li>3 – awake, inactive </li></ul><ul><ul><li>Eyes fully open, head up, no locomotion or rearing, normal posture </li></ul></ul><ul><li>2 – moderate sedation </li></ul><ul><ul><li>Eyes partly closed, head somewhat down </li></ul></ul><ul><li>1 – heavy sedation </li></ul><ul><ul><li>Eyes mostly closed, head mostly or completely down, flattened posture, lack of normal limb placement </li></ul></ul><ul><li>0 – asleep </li></ul><ul><ul><li>Eyes fully closed, body relaxed, loss of righting reflex </li></ul></ul>Salamone et al. 1996
  32. 35. Hypotheses <ul><li>Ethanol infused into the SNr will have an activating effect on locomotor behavior at low doses </li></ul><ul><li>Acetaldehyde infused into the SNr will also produce an activating effect, and will be more potent than ethanol </li></ul><ul><li>Acetate infused into the SNr will not increase motor activity and may produce a suppressive effect on activity </li></ul>
  33. 36. Hypotheses (continued) <ul><li>The behavioral activating effect of ethanol infused in the SNr can be blocked with peripheral administration of a catalase inhibitor. The catalase inhibitor will have no effect on acetaldehyde-induced behavioral activation </li></ul>
  34. 37. Hypotheses (continued) <ul><li>Low doses of ethanol and acetaldehyde infused into the SNr will not produce ataxia </li></ul><ul><li>Of all three compounds studied, acetate is the most likely produce ataxia in the dose range tested </li></ul><ul><li>Locomotor activity and ataxia are dissociable and are being produced through 2 different mechanisms </li></ul>
  35. 38. <ul><li>The results of the proposed experiments will further elucidate the brain mechanisms and biochemical pathways through which ethanol exerts some of its behavioral effects. </li></ul>
  36. 40. <ul><li>Effects on neurotransmission </li></ul>GABA. Like benzodiazepines, barbiturates and anesthetics, acute ethanol enhances GABA’s influence on GABA A receptor thus facilitating Cl- influx. (10-50 mM). This process seems to be mediated by the phosphorylation induced by PKC (protein kinase C). Chronic ethanol administration produces the opposite effects on GABA A receptors and reduces the synthesis of one of protein subunits of this receptor. Glutamate. Acute administration inhibits NMDA receptor/cation channel complex (20-50 mM). This inhibition interferes with excitotoxicity in cortex, and with LTP in the hippocampus. Chronic administration increases NMDA receptor numbers.
  37. 41. DA. Acute and Chronic alcohol administration induces dopamine release in the N. Accumbens. 5-HT. Acute ethanol induces the release of serotonin and facilitates the cation-5-HT 3 -gated channel (10-50 mM). Chronic alcohol increases the number of 5-HT 2. <ul><li>Effects on neurotransmission </li></ul>
  38. 42. Endogenous Opioids . Acute alcohol increases endorphin and enkephalin expression and release. Chronic alcohol produces the opposite effects. Adenosine . Acute alcohol increases extracellular adenosine by inhibiting adenosine uptake, and increases synthesis of adenosine. The activation of the A 2 receptor increases intracellular cAMP. Chronic alcohol produces the opposite effects. <ul><li>Effects on neurotransmission </li></ul>
  39. 43. Evidence of central ethanol metabolism by Catalase. <ul><li>Catalase is widespread in brain, and also is localized in several discrete brain nuclei. </li></ul><ul><li>In vivo and in vitro administration of catalase inhibitors blocks acetaldehyde formation in different brain nuclei. In contrast, when H2O2 concentration is increased, acetaldehyde fomation also increases. </li></ul><ul><li>Acatalasemic mice mutants have less ethanol-induced locomotor activity, more ethanol-induced sleep, and higher ethanol consumption. </li></ul><ul><li>The pharmacological inhibition or potentiation of catalase modifies some acute ethanol-induced effects as well as the ingestion of ethanol. </li></ul>

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