CNS N27 Flashcards by Jennifer Becker

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

Cocaine effect Dopamine by

preventing reuptake

Reserpine effect Dopamine by

interferes with storage

MAO inhibitors effect Dopamine by

preventing breakdown of DA

Bromocryptine

Agonist to the postsynaptic receptor

Haloperidol

antagonist to the postsynaptic receptor

Methylxanthenes (caffeine)

many effects on postsynaptic cell (increased cAMP)

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

Neurotransmitter: Catecholamines

Norepinephrine, epinephrine, dopamine

Neurotransmitter: Indolamines

serotonin

Neurotransmitter: Amino acids

GABA, glycine, aspartic acid, glutamic acid

Neurotransmitter: AcH and histamine

acetylcholine and histamine

Neurotransmitter: Opioid Peptides

met enkephalin, leu enkephalin, beta-endorphin, dynorphin

Miscellaneous Neurotransmitters

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

Neuromodulator

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

Neurohormones

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

Acetylcholine receptors

Nicotinic and muscarinic

Acetylcholine locations

CNS, preganglionic ANS, postganglionic PSN

Dopamine receptors

D1-D5

Dopamine locations

brainstem, coritcal, limbic, extrapyramidal, and endocrine areas

Serotonin receptors

5-HT1 - 5-HT3

Serotonin location

pons, midbrain, reticular formation

function of Acetylcholine

learning, memory, ANS

Function of Dopamine

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

Function of Serotonin

Sleep-wake cycle, feeding, sensory processing, mood

Chronic use of drugs leads to 2 things

drug tolerance and drug dependence

Drug tolerance

decreased sensitivity to drug

Pharmacokinetic (drug dispositional) tolerance

induction of enzymes that metabolize the drug

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

Drug Dependance

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

Drug Addiction

drug use interferes with life

Physical and Psychological dependence

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

Physical Dependence

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

Cross dependence

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

Cross tolerance

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

Sympathomimetic effects

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

Sympatholytic effects

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

Parasympathomimetic effects

increased cholinergic transmission in CNS and increased cholinergic transmission of PNS

Parasympatholytic effects

decreased cholinergic transmission in CNS and decreased cholinergic transmission in PNS