NSCI 110 1st Edition Final Exam Study Guide Lectures 14 23 Chapter 6 How Do Drugs and Hormones Influence the Brain and Behavior A drug s route of administration is how it enters and reaches its nervous system target in the body o Oral administration is the most complex route Must be absorbed by the stomach or small intestine if they can be dissolved by the stomach s gastric juices Then enters the bloodstream where it must be water soluble o Inhalation provides quick absorption into the respiratory tract o With each obstacle eliminated on the way to the brain a drug s needed dosage decreases by a factor of 10 This is why drugs that are inhaled or injected are cheaper per dose The blood brain barrier consists of tight junctions between capillaries o Protects brain s ion concentration and prevents unwanted substances from entering Capillaries consist of a single endothelium layer Substances normally may pass through clefts in between these cells However in the brain they are fused to form tight junctions to limit passage Are covered with astrocyte feet o Oxygen and carbon dioxide and other small uncharged molecules may pass through the BBB endothelial membrane Larger molecules like glucose amino acids and fats are carried across by active transport systems or pumps o 98 of drugs that have the ability to affect brain function cannot cross the BBB How the body eliminates drugs o Drugs are diluted once in the bloodstream but may accumulate in fat cells May be catabolized in the kidneys liver intestine o Excreted in urine feces sweat exhaled air Therapeutic drugs are designed to have prolonged survival time in the body o The liver can catabolize many drugs so they may be more easily excreted Drugs may regulate any of the following processes involving synaptic activity o Synthesis of the transmitter in the cell body axon or terminal o Storage of the transmitter into vesicles or granules o Release of the transmitter into the synapse o Receptor interaction on the postsynaptic membrane o Inactivation of removal or excess transmitter in the synapse o Reuptake into the presynaptic terminal o Degradation of excess transmitter in the synapse Tolerance is a decreased response to a drug after repeated exposure o Metabolic tolerance involves the number of enzymes responsible for catabolizing a substance increasing Results in quicker metabolizing of substances o Cellular tolerance involves the activities of cells adjusting to minimize the drug s effects Explains why there can be minimal intoxication signs with a high blood alcohol level o Learned tolerance involves learning to cope with the drug s effects so that they are not as easily noticed Sensitization involves increased responses to repeated drug exposure o May be due to more release of transmitter in exposed individuals Also changes in the number of postsynaptic receptors the rate of metabolism in the synapse and the number size of synapses o Responses can be enhanced when the environment changes The categorization of psychoactive drugs is according to their most pronounced behavioral effects o Group I antianxiety agents and sedative hypnotics At low doses they reduce anxiety Medium doses sedate High doses anesthetize or induce coma Antianxiety drugs are safer at higher doses than sedatives Antianxiety agents minor tranquilizers include benzodiazepines Aid sleep and produce relaxing effects Sedative hypnotics include alcohol and barbiturates Barbiturates mainly used for anesthesia before surgery Exhibit tolerance Both members of this group target GABA receptors Excitation causes chloride ions to influx producing an inhibitory effect There may be specific barbiturate or benzodiazepine sites on GABA receptors causing pore to be open longer or increasing the binding of GABA Their effects can summate so they should not be taken together Drugs that act on GABA receptors may affect brain development o Group II antipsychotic agents First generation antipsychotics FGAs block dopamine receptors Second generation SGAs block dopamine and serotonin receptors o Group III antidepressants and mood stabilizers Association between vitamin D deficiency and depression Three types of antidepressants all are serotonin agonists Monoamine oxidase MAO inhibitors o Inhibit an enzyme that catabolizes serotonin in the axon terminal Tricyclic antidepressants o Block serotonin reuptake Second generation antidepressants o Block serotonin reuptake Are thought to stimulate second messengers that result in repairing of stress damaged neurons o Take weeks to have full effects Mood stabilizers attempt to treat bipolar disorder by muting one pole of the disorder making the other pole less likely to occur Lithium o Group IV opioid analgesics Opioids bind to receptors that are sensitive to morphine Also called narcotic analgesics Have sleep inducing and pain relieving effects In addition to relaxation euphoria constipation Two natural sources of opioids Opium extract of seeds of the opium poppy o Morphine and codeine are derived from opium Source found in the brain as endorphins o Three classes Competitive inhibitors may compete with opioids for receptors preventing overdoses Are long acting Produce a tolerance that requires a tenfold increase in dosage after successive uses Morphine may result in tolerance or sensitization o Group V psychotropics Affect mental activity motor activity arousal perception and mood Behavioral stimulants increase motor behavior elevate mood and alertness Amphetamine and cocaine Psychedelic and hallucinogenic stimulants Alter sensory perception and cognitive processes THC acts on endogenous receptors for anandamide PCP ketamine NMDA block glutamate receptors Mescaline blocks norepinephrine receptors LSD and mushrooms block serotonin receptors General stimulants cause an overall increase in metabolic activity in cells Caffeine inhibits an enzyme that breaks down cAMP causing an increase in glucose production higher metabolic rate in cells o The effect on behavior by drugs Disinhibition theory alcohol depressed learned inhibitions such as reasoning and judgment Context environment affects behavior as well Immediate cues overpower long term consequences Substance abuse involves the reliance on a drug where it distracts them from normal life Advanced state is addiction May experience physical withdrawal symptoms Many addictive drugs produce psychomotor activation in their dosage range Make the user feel energetic and in control All act on dopamine