Chapter 6 - Drugs and Hormones Flashcards
psychopharmacology
the study of how drugs affect the nervous system and behavior
psychoactive drugs
substances that cause changes in moods, thoughts, or behaviors
- used to treat neurophysiological disorders, or taken recreationally
- sometimes abused
routes of administration
enteral:
- via the digestive system
- have a slower effect because they must cross more barriers before reaching the CNS
parenteral:
- not via the digestive system
enteral routes of administration
- oral: through the mouth (most convenient but slow)
- rectal: through the rectum
- gastric: through the stomach
- buccal/sublabial: between lips and gums
- sublingual: under the tongue
parenteral routes of administration
- subcutaneous: injecting the drug just below the skin
- intramuscular: injecting the drug into the muscle
- transdermal: using patches to administer the drug through the skin
- inhalation: breathing in the drug
- intravenous: injecting the drug into veins
- spinal or intracranial: directly into the CNS (fastest route and only low doses needed)
order of routes of administration (slowest to fastest)
- oral
- transdermal/intramuscular
- inhalation
- intravenous
- spinal/intracranial
blood-brain barrier
drugs must escape from the bloodstream and enter the brain’s extracellular fluid to be active in the brain
- however the passage of the drug from blood to the brain is hampered by the blood-brain barrier (the tight junctions between the cells of blood vessels in the brain that block the passage of most substances)
3 areas in the brain which do not have the blood-brain barrier
- pituitary gland: its main purpose is to release hormones into the blood, and hormone release is triggered in part by other hormones carried to the pituitary by the blood
- area postrema (in the brainstem): it detects toxic substances in the blood and triggers vomiting to expel any potential toxins still in the stomach
- pineal gland: it regulates the day/night cycle based in part on hormones that reach it through the blood
how are pharmaceuticals removed from the body?
through the liver, kidneys, and intestines
- catabolized or broken down by cytochrome P450 enzyme in the liver or biole in the intestines
- excreted by urine, faeces, sweat, breastfeeding, and exhaled air
- substances not excreted can become poisonous
steps of drug neurotransmission
- synthesis
- storage
- release
- receptor interaction
- inactivation
- reuptake
- degradation
synthesis
the production of a neurotransmitter can take place in the cell body, the axon, or the terminal
neurotransmitters are made in 2 ways:
- made in the cell body and transported on microtubules to the axon terminal
- made in the axon terminal from building blocks derived from food
storage
storage of the neurotransmitter takes place in granules, vesicles, or both
release
the release of the neurotransmitter is from the terminal presynaptic membrane into the synapse
receptor interaction
the receptor interaction takes place in the post-synaptic membrane when the transmitter operates on an embedded receptor
inactivation
inactivation of the neurotransmitter can occur via reuptake or degradation
reuptake
the reintegration in the presynaptic terminal for re-use
degradation
the degradation of a surplus of neurotransmitters by synaptic mechanisms and removal of unnecessary by-products from the synapeses is another procedure
agonist drug
mimics or enhances the effect of a neurotransmitter
antagonist drug
operates against the effect of a neurotransmitter
tolerance
the reduction of a response to a drug by repeated exposure
- drugs are broken down within the body
- the reaction to a substance decreases with time
3 mechanisms in which the body adapts to intake of non-body substances
- metabolic tolerance: the number of enzymes needed to break down the drug in the liver, blood, and brain increases more rapidly
- cellular tolerance: the activity in the brain cells adapts to minimize the effects of the drug in the blood
- learned tolerance: people learn to live with the demands of living with a standard intake of the drug and they learn to gradually expand their intake threshold
sensitization
sensitization to a drug is an increased responsiveness to equal doses
- mainly developed by intermittent drug use, and can lead to addiction
- neural basis of sensitization lies partly in the changes in the synapse
- tied to novel cues in the environment (e.g. being in an unfamiliar environment while taking the drug)
psycholeptics
substances that inhibit psychological functions
sedatives, hypnotics, anxiolytics
- GABA is generally an inhibitor
- alcohol and anti-anxiety medication should never be taken together
antipsychotics, “neuroleptics”
- dopamine (DA) is generally activating
- used to treat schizophrenia
psychoanaleptics
substances that stimulate psychological functions
antidepressants
- serotonin (SE) is generally activating
- monoamine oxidase (MAO) inhibitors, tricyclic antidepressants (TCA), selective serotonin reuptake inhibitors (SSRIs)
stimulants (cocaine, amphetamine, MDMA)
- dopamine (DA) is generally activating
psychodysleptics
substances that disorganize psychological functions
narcotic analgesics (heroin, morphine, beta-endorphin)
- highly addictive, sleep-inducing, pain-relieving
hallucinogens, “psychedelics” (magic muschrooms, LSD, cannabinoids)
- non-specific amplifiers whose effects depend on the mood, intention, and surroundings of the person taking them
factors influencing individual responses to medication
- disinhibition theory
- learning
- behavioral myopia
disinhibition theory
alcohol affects the judgment-making and impulse-controlling areas of the brain (cortex) while sparing the areas related to instinctual behaviors like aggression and desire (subcortical regions)
learning
behavior on drugs depends on the context, culture, group, and setting
behavioral myopia
the tendency for people on drugs to respond to immediate and salient cues while ignoring more distant cues and possible consequences
substance abuse
a pattern of drug use in which people have chronic and excessive reliance on a drug, placing it at the heart of their lives
withdrawal symptoms
negative symptoms experienced when people with a drug addiction stop taking the drug
psychomotor activation
at certain consumption levels, the drugs make the user feel energetic and in control
the wanting-and-liking theory (Robinson and Berridge (2008))
based on the idea that wanting and liking are produced by different brain systems
- ‘wanting’ is the craving for the drug, and ‘liking’ is the pleasure produced by the drug
- with repeated use, a tolerance for liking and a sensitivity for wanting develop, so the expression of pleasure decreases while craving increases
hormones
chemical messengers
- produced by glands and then absorbed into the bloodstream and distributed throughout the body
endocrine system
the network of glands and organs in which hormones are active
steroid hormones
such as testosterone and cortisol, are made from cholesterol in glands and are fat soluble
- can directly influence gene transcription (DNA)
peptide hormones
such as insulin and endorphin, are made by cellular DNA in the same way as other proteins
- indirectly influence gene transcription by binding to a metabotropic receptor on the cellular membrane and activating a second messenger
3 main functional groups of hormones
- homeostatic hormones
- gonadal (sex) hormones
- glucocorticoids (stress hormones)
homeostatic hormones
hormones that try to maintain a state of internal metabolic balance, just like a thermostat in a living room
- e.g. insuling maintaining a constant level of glucose in the blood
gonadal (sex) hormones
hormones that control reproductive functions and stimulate the body to develop either as male (testosterone) or female (estrogen)
- gonadal hormones also influence sexual behavior and conception
- some gonadal hormones regulate the menstrual cycle (oestrogen and progesterone), the pregnancy process, and breastfeeding (prolactin, oxytocin)
glucocorticoids (stress hormones)
steroid hormones that are released in times of stress and help the body prepare to fight or flee
- e.g. cortisol
2 pathways of the adrenal gland
- fast pathway
- slow pathway
fast pathway of the adrenal gland
- activates in seconds
- hypothalamus sends a neural message through the spinal cord
- sympathetic division (fight or flight) of the ANS is activated and stimulates the medulla of the adrenal gland
- parasympathetic division is switched off
- adrenal medulla releases epinephrine (adrenaline) into the bloodstream
- epinephrine activates the body cells, endocrine glands, and the brain
slow pathway of the adrenal gland
- activated in minutes to hours
- hypothalamus releases the hormone CRH (corticotropin-releasing hormone) into the pituitary gland
- pituitary gland releases the hormone ACTH into the bloodstream, which acts on the cortex of the adrenal gland
- adrenal cortex releases the glucocorticoid hormone cortisol into the bloodstream and the cortisol activates body cells, endocrine glands, and the brain
