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Flashcards in CNS N27 Deck (63)
1

Major site for drug toxicity

CNS

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Empirical approach to drugs

stumble upon a drug that treats symptoms, leads to research on mechanism of underlying disease

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Rational approach to drugs

know mechanism of disease, develop drugs to treat disease

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Lipophilic drugs for CNS

brain is 50% fat, so most drugs are lipophilic

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Brain receives _____ of cardiac output

high percentage

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Blood Brain Barrier

tight junctions of endothelial cells + foot pedicels of astrocytes

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Blood Brain Barrier inhibits particle diffusion for which 3 characteristics

Size (< 1000)
Charge (neutral)
Metabolic susceptibility (not metabolized by MAO and COMT)

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Drugs mainly cross the BBB by

simple diffusion; they are small (<1000), uncharged, lipid soluble, resistant to metabolic breakdown

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2 types of cells found in the brain

Glia and Neurons

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Glia

support neurons + complex role

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Neurons

processing of information; drugs work by altering neuronal function

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Electrical Conduction

along cell surface and axon

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Transmission

across synapses via neurotransmitters

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3 types of signal transmission

Adenylate Cyclase (cAMP)
Phosphoinositide (IP3)
Alteration of intracellular ion conc. (Na, Ca, K , Cl)

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Agonist

drugs that mimic the action of a transmitter

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Antagonist

drugs that block the receptor

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Enhancers of reducer drugs

enhance or reduce the effects of transmitters

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Example of an agonist

Beta-agonist that mimics epinephrine to increase the rate or force of contraction

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Example of an antagonist

Beta-antagonist (propranolol) competitively blocks the epinephrine receptor and prevents actions of epinephrine and other agonists

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GABA receptor mechanism

GABA binds receptor --> Cl channels open --> influx of Cl --> hyperpolarization --> decreased neuronal firing

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Benzodiazepines

used in anxiety, as sedative, anticonvulsant, muscle relaxant; bind a distinct receptor on the Cl channel and enhance the effect of GABA

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Barbituates

may also enhance GABA

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Dopamine Mechanism

synthesized from tyrosine, AP --> release of DA into cleft--> effect in target cell--> terminated by reuptake

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I-DOPA effect Dopamine by

effecting the uptake and synthesis (increasing DOPA action)

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Amphetamines effect Dopamine by

stimulating release

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Cocaine effect Dopamine by

preventing reuptake

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Reserpine effect Dopamine by

interferes with storage

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MAO inhibitors effect Dopamine by

preventing breakdown of DA

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Bromocryptine

Agonist to the postsynaptic receptor

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Haloperidol

antagonist to the postsynaptic receptor

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Methylxanthenes (caffeine)

many effects on postsynaptic cell (increased cAMP)

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Neurotransmitter criteria

present in presynaptic cell, release upon stimulation, stimulation of nerve has consistent effect, antagonists must block the effects, means of terminating action of agent

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Neurotransmitter: Catecholamines

Norepinephrine, epinephrine, dopamine

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Neurotransmitter: Indolamines

serotonin

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Neurotransmitter: Amino acids

GABA, glycine, aspartic acid, glutamic acid

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Neurotransmitter: AcH and histamine

acetylcholine and histamine

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Neurotransmitter: Opioid Peptides

met enkephalin, leu enkephalin, beta-endorphin, dynorphin

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Miscellaneous Neurotransmitters

Substance P, vasoactive intestinal peptide (VIP), cholecystokinin (CCK)

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Neuromodulator

influences neuronal function but is not considered a neurotransmitter (prostaglandins, peptides)

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Neurohormones

released from neurons and act as endocrine hormones (beta-endorphin)

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Acetylcholine receptors

Nicotinic and muscarinic

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Acetylcholine locations

CNS, preganglionic ANS, postganglionic PSN

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Dopamine receptors

D1-D5

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Dopamine locations

brainstem, coritcal, limbic, extrapyramidal, and endocrine areas

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Serotonin receptors

5-HT1 - 5-HT3

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Serotonin location

pons, midbrain, reticular formation

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function of Acetylcholine

learning, memory, ANS

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Function of Dopamine

complex thought, motor function, regulation, reward mechanism, mood

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Function of Serotonin

Sleep-wake cycle, feeding, sensory processing, mood

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Chronic use of drugs leads to 2 things

drug tolerance and drug dependence

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Drug tolerance

decreased sensitivity to drug

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Pharmacokinetic (drug dispositional) tolerance

induction of enzymes that metabolize the drug

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Pharmacodynamic tolerance

changes in sensitivity to dugs due to change sin the number of receptors or changes in the sensitivity of the receptor-effector mechanism

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Drug Dependance

Physiological changes in the body that occur with drug use, so that when the drug is stopped physical withdrawal signs occur

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Drug Addiction

drug use interferes with life

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Physical and Psychological dependence

Once believed to be separate, but now believed to be interrelated

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Physical Dependence

physiological adaptation to chronic drug exposure (tolerance also occurs (pharmacodynamic and pharmacokinetics))

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Cross dependence

use of a lesser drug to prevent withdrawal symptoms from a more severe drug

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Cross tolerance

tolerance to 1 drug may cause tolerance to another drug to increase

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Sympathomimetic effects

drugs may affect CNS and periphery; stimulation of NE in CNS will also cause STIMULUATION of NE in the SNS

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Sympatholytic effects

drugs that inhibit NE transmission in the CNS may also cause INHIBITION of NE in the SNS

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Parasympathomimetic effects

increased cholinergic transmission in CNS and increased cholinergic transmission of PNS

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Parasympatholytic effects

decreased cholinergic transmission in CNS and decreased cholinergic transmission in PNS