Psychological disorders Flashcards
Drug Mechanisms
- Drugs either facilitate or inhibit transmission at synapses.
a. Antagonists block receptors, while agonists mimic or increase effects of a neurotransmitter.
b. A drug has an affinity for a receptor if it binds to it (like a key in a lock).
c. A drug’s efficacy is its tendency to activate the receptor.
Similarities and Differences Among Addictive Substances
Nearly all abused drugs increase activity at dopamine and norepinephrine synapses.
b. Discovery of neuroanatomy of addiction occurred by accident, when Olds & Milner missed a target for implanting an electrode in rats. The rats’ self- stimulation of the brain increased when electrodes were in areas that increased the release of dopamine or norepinephrine in the nucleus accumbens.
c. Nucleus accumbens
reinforces experiences of all types; drugs work to increase dopamine in that area via direct (stimulants) or indirect (opiates) means.
- All abused drugs and even non-drug addictions such as gambling have much in common
A craving
is an insistent search for an activity.
Tolerance
occurs when the effects of a drug (especially the pleasurable effects) decrease over time.
b. Tolerance is in part learned; when rats are given a drug in a location, their tolerance is increased in that location.
c. When the body reacts to the absence of a drug, it is called withdrawal.
Type II (or Type B) alcoholism
has a rapid onset, usually before 25. Most are men with a family history of alcoholism
Type I (or Type A) alcoholism
develop alcohol problems gradually, after 25. The late-onset type depends more on stressful life and less on genetics and is generally less severe and more responsive to treatment
Antabuse
makes it harder to metabolize acetaldehyde, which causes a person to feel sick after drinking alcohol.
Methadone and LAAM
are used to reduce withdrawal and avoid the “high” of heroin and morphine. They do not end opiate addiction, but satisfy the craving in a less dangerous way.
Major Depression:
People with major depression feel sad, helpless, and lacking in energy and pleasure for weeks at a time. Individuals with major depression also feel worthless, have trouble sleeping, cannot concentrate, get little pleasure from sex or food, may contemplate suicide, and in many cases, can hardly imagine being happy.
Types of Antidepressants
a. Tricyclics
b. Selective serotonin reuptake inhibitors (SSRIs)
c. Serotonin norepinephrine reuptake inhibitors (SNRIs)
d. Monoamine oxidase inhibitors (MAOIs
e. Atypical antidepressants
Tricyclics:
Prevent the presynaptic neuron from reabsorbing serotonin, dopamine and norepinephrine after releasing them (this allows the neurotransmitter to remain longer in the synaptic cleft thus stimulating postsynaptic receptors). But causes side-effects such as drowsiness (because it also blocks histamine), dry mouth, difficulty urinating and heart irregularities (and blocks acetylcholine)
Selective serotonin reuptake inhibitors (SSRIs):
These drugs are similar to tricyclics, but are specific to the neurotransmitter serotonin. The most popular drug in this class is fluoxetine (Prozac). Produce fewer side effects than tricyclics
Serotonin norepinephrine reuptake inhibitors (SNRIs):
Block the reuptake of serotonin and norepinephrine. Produce fewer side effects than tricyclics
Monoamine oxidase inhibitors (MAOIs):
Block the enzyme monoamine oxidase (MAO) from metabolizing catecholamines and serotonin into inactive forms. Was the earliest antidepressants, but now is only used when tricyclics or SSRIs do not work because people need to avoid foods containing tyramine (cheese, raisins and many others)
Atypical antidepressants:
A miscellaneous group of drugs with antidepressant actions and mild side effects, including bupropion (Wellbutrin), which inhibits reuptake of dopamine and to some extent norepinephrine.
Why are Antidepressants Effective?
One theory is that most people with depression have lower than average levels of a neurotrophin called brain-derived neurotrophic factor (BDNF) that is important for synaptic plasticity, learning and the proliferation of new neurons in the hippocampus. Many studies suggest antidepressants increase BDNF over the course of weeks (consistent with the course for antidepressants to take effect). The capacity to make new neurons makes it easier to learn new ways of coping.
Exercise as therapy:
Regular, non-strenuous exercise increases blood flow to the brain and provides other benefits that are especially helpful to people with depression such as increases in levels of serotonin and BDNF.