1Biopsychology 2012 – sec 001 Study Guide for Section 4 (last section) Psychoactive Drugs and Addiction What are psychoactive drugs? Substances that influence subjective experience and behavior by acting on the nervous system. What are some of the most common psychoactive drugs? 1. Sedative hypnotics and anxiolytics (antianxiety drugs) 2. Antipsychotic drugs 3. Antidepressant drugs 4. Opiates (analgesics) 5. Stimulants I. Sedative hypnotics and anxiolytics: Most common: 1. Alcohol 2. Barbiturates (ex. pentobarbital, sodium amytal – truth serum) 3. Benzodiazepines (ex., valium™, librium™) Also known as “mild tranquilizers” How do sedative hypnotics and antianxiety drugs work? They bind to the GABAA receptor complex and facilitate the action of the endogenous neurotransmitter GABA. II. Antipsychotic drugs: used to treat psychotic conditions such as schizophrenia, paranoia, etc. Most common 1. Phenothiazines (ex., chlorpromazine - Thorazine™) 2. Butyrophenones (ex., haloperidol - Haldol™) Also known as “major tranquilizers” How do antipsychotics work? They block dopamine receptors, especially the D2 receptor subtype. III. Antidepressant drugs: used to treat depressive illnesses Most common 1. Monoamine oxidase inhibitors (MAOI) 2. Tricyclics antidepressants (ex., imipramine - Tofranil™) 3. Serotonin-specific reuptake inhibitors (SSRIs ex., fluoxetine - Prozac™) How do antidepressants work? MAOIs and tricyclics/SSRIs work through different mechanisms: - MAOIs block the breakdown of monoamines neurotransmitters (especially serotonin and noradrenaline) - Tricyclic antidepressants and SSRIs block the reuptake of monoamines (especially serotonin and noradrenaline – with the SSRIs being more specific for serotonin) - Overall then, all antidepressant drugs increase the amount of monoamine neurotransmitters in the synapses2IV. Opiates (analgesics): clinically used in the treatment of pain – high potential for addiction Most common: 1. Opium poppy derivatives (ex., morphine, codeine) 2. Derivatives of morphine (ex., heroin) 3. Endogenous morphine (endorphins) = made in the body (ex., enkephalins, dynorphin, β-endorphin) How do opiates work? All work by binding opiate receptors in the nervous system (mu, delta, and kappa subtypes of opiate receptors) V. Stimulants: in general, increase the activity of the nervous system Several classes of stimulants: 1. Behavioral stimulants (ex., cocaine, “crack”, amphetamine) 2. Convulsant stimulants (ex., pentalenetetrazol, bicuculline) 3. General stimulants (ex., caffeine) 4. Pscychedelics (ex., lysergic acid diethylamide [LSD], mescaline, marijuana, ecstasy, psilocybin [from some mushrooms]) How do stimulants work? Each subtype has different mechanism of action: - Behavioral stimulants generally work by blocking dopamine reuptake at the synapse and some even produce dopamine release (amphetamine). - Convulsants block GABA receptors. - A general stimulant such as caffeine works by blocking one subtype of adenosine receptor - Psychedelic drugs have various mechanisms of action which involve the serotonin system (LSD, ecstasy, mescaline, psilocybin) or other specific neurotransmitter receptors (the cannabinoid receptor for marijuana). What is addiction? Someone addicted to a drug is, in a way, sentenced to a term of involuntary servitude, being obliged to fulfill the demands of their drug dependency What is drug tolerance? Decreased susceptibility to a drug that develops as a result of repeated exposure to the drug; mostly mediated by compensatory mechanisms that oppose the initial drug effect (ex., if drug causes hypothermia, opposing mechanism of hyperthermia is produced) What is cross-tolerance? tolerance that develops to one drug carries over to other drugs (often of the same family) suggesting that they act through the same target (mechanism) What are the 3 different types of tolerance that we discussed in class? 1. Metabolic tolerance: reduced sensitivity to a drug that results from the increased ability of the body to metabolize the drug (ex., up-regulation of liver enzymes) 2. Cellular tolerance: a change that takes place in nerve cells in which the activity of neurons adjust to the exctitatory or inhibitory effects of a drug (ex., receptor downregulation) 3. Learned tolerance: behavior change acquired through associative learning. What is physical dependence? State in which discontinuation of drug taking will induce withdrawal syndrome (illness)3What is the withdrawal syndrome? Illness induced by the elimination or absence from the body of a drug on which a person is physically dependent. What is psychological dependence? The most important factor in addictive behavior – includes several cues associated (conditioned) with pleasurable effects of drugs that are difficult to eliminate; mostly responsible for “compulsive” drug taking behaviors. What is sensitization? Increased behavioral response to the same dose of a drug - for example, the behavioral activity of animals in response to repeated injections of amphetamine increases over time. What is the role of learning in addiction? Involved in the development of psychological dependence. 1. Associations of places and cues with drug taking produces both conditioned drug tolerance and conditioned withdrawal effects (Siegel). Example: Rats that are injected with morphine repeatedly in context A will develop conditioned tolerance and withdrawal only in context A, not in their homecage. Thus, if they get injected with a high dose of morphine in their homecage, they are much more vulnerable to die from an overdose, than if they received the injection in context A. What is reinforcement? Process by which there is an increase in the likelihood of a behavior immediately preceding the reinforcement (positive or negative). Reinforcement is most effective upon behaviors that have just happened – it’s effects wane very quickly with time (example of rats preferring a small reward immediately rather than a much larger reward, with a delay). Who discovered reinforcement? In a classic study, Olds & Milner (1954) implanted electrodes in the brain of rodents that were aimed for the reticular formation, but accidentally implanted some animals in the medial