1. Psychopharmacology psychopharmacology – study of drugs and behavior
Drugs and behavior – PSY 459
some general concepts and issues
psychoactive drugs – change the way you feel

2. Why do people take psychoactive (particularly illicit) drugs?
To feel good
(positive reinforcement – likely cause DA release!)
psychological dependence
**greatest amount of psychological dependence occurs if the rewarding effects of drugs happen very quickly after behaviors associated with them.

3. drug rewards that happen very soon after a
behavior – strong positive reinforcement for
that behavior
ex. prep for heroin injection, crack smoking, etc.

4. Why do people take drugs?
2. To avoid feeling bad (reduce withdrawal)
(negative reinforcement)
chemical dependence

5. Important issues related to how and why we take drugs
pharmacokinetics:
includes drug absorption, distribution, metabolism and drug excretion
absorption – how we take drugs into the body
distribution - how the drug reaches its primary site of action
metabolism - how our body breaks drugs down
excretion - how we eliminate drugs

6. pharmacokinetics....... how a drug is taken into the body……
for drugs of abuse - the more rapidly the drug gets to the brain – the greater the abuse liability!

7. routes of administration
oral
injection
subcutaneous
intramuscular
intravenous - reaches brain in ~ 10 secs
quick response but also most dangerous
inhalation - reaches brain in ~8 secs
dermal – absorbed through the skin
buccal or nasal membranes

8. pharmacokinetics....... 2. absorption –
all drugs that change how we feel must be able to cross the blood brain barrier
3. pharmacodynamics
how does drug produce its effects on behavior (ie what neurotransmitter or neurotransmitters are affected)

9. ex of pharmacodynamics –
1. cocaine – blocks reuptake of monoamine neurotransmitters (most important DA)
2. nicotine
acts as an agonist at nicotinic cholinergic receptors
3. alcohol
works on virtually every neurotransmitter

10. 4. metabolism (detoxification or breakdown)
how a drug is broken down or made into inactive forms
mostly done by the liver – via enzymes!

11. Tolerance, Dependence, Withdrawal, etc……
tolerance – either decreased effectiveness or potency of a drug

12. Mechanisms for Tolerance
metabolic tolerance –
enzyme induction-
enzymes – speed up a chemical reaction
with repeated exposure, enzymes get better at breaking down drug or liver makes more enzymes

13. Mechanisms for Tolerance
metabolic tolerance –
enzyme induction- enzymes are either better at breaking down drug or liver makes more of them
implications?

14. Mechanisms for Tolerance
metabolic tolerance –
enzyme induction
cross tolerance – tolerance to one drug results in tolerance to other drugs (usually that need similar enzymes for breakdown)
Implications:

15. Mechanisms for Tolerance
cross tolerance – tolerance to one drug results in tolerance to other drugs (usually that need similar enzymes for breakdown)
Implications:
Person shows up unconscious at ER and is an alcoholic – given a barbiturate for surgery;

16. What if amount of drug reaching brain/body is unchanged?
tolerance can still occur when the amount of drug reaching the brain/body is unchanged
pharmacodynamic or physiological tolerance –

17. What if amount of drug reaching brain/body is unchanged?
pharmacodynamic or physiological tolerance –
“for every action, there is an equal and opposite
reaction (in your brain)”

18. Ways that the brain may try and compensate……
Use alcohol as an example –
Acutely – alcohol decreases glutamate activity and increases GABA activity
Chronic alcohol brain’s compensatory response?

19. How might the brain try and compensate for this change if it is chronic?
upregulation of GLU receptors –
increase the number or sensitivity of glutamate receptors to compensate for decreased activity and try to get activity back to normal levels….

20. How might the brain try and compensate for this change if it is chronic?
upregulation of GLU receptors –
increase the number or sensitivity of glutamate receptors to compensate for decreased activity and try to get activity back to normal levels….
what happens during alcohol withdrawal?
now have too many (or too sensitive) glutamate receptors – overexcitation, seizures, etc.

21. How might the brain try and compensate for this change if it is chronic?
down regulation of GABA receptors –
to compensate for increased activity and try to get activity back to normal levels…. – reduce n or sensitivity of GABA receptors

22. How might the brain try and compensate for this change if it is chronic?
down regulation of GABA receptors –
to compensate for increased activity and try to get activity back to normal levels…. – reduce n or sensitivity of GABA receptors
what happens during alcohol withdrawal?

23. Explanation for various withdrawal symptoms
the exposure of compensatory changes in brain (and body perhaps) likely explain a number of withdrawal symptoms (that are often opposite of the effects that the drug causes)

24. chemical see-saw
drug
brain response

25. chemical see-saw
heroin
constipation

26. heroin WD
diarrhea

27. Environmental Tolerance
Drugs taken in the same environment can also display tolerance associated with the conditioned cues
ex. heroin
explanation – compensatory changes in brain in EXPECTATION of drug

28. 5. excretion (elimination)
how a drug once broken down (or not) is eliminated from body
most psychoactive drugs metabolites excreted in urine