Chapter #4: How do drugs affect our behavior? Flashcards
Agonist
an endogenous ligand (a naturally occurring molecule such as a transmitter that binds to the receptor) that activates its cognate receptor
Receptor Agonist
an exogenous ligand (a drug or toxin) that resembles the endogenous ligand and is capable of binding to the receptor and activating it
Competitive Antagonist
substances that bind to the receptor, but do not activate it; they block agonists from binding to the receptors
Noncompetitive Antagonist
agonist or antagonist drugs that bind to target receptors at a site that is different from where the endogenous ligand binds
if a particular drug has low affinity for a receptor…
-it will quickly uncouple from the receptor
-to bind half the receptors at any given time, a higher concentration of the drug is needed
if a drug has a high affinity for a receptor…
-the two will stay together for a longer time
-a lower concentration of drug will be sufficient to bind half the receptors
if equal concentrations of the two drugs are present…
-the high-affinity drugs will be bound to more receptors at any given time
-if the drugs have an equivalent effect on the receptors, then the higher-affinity drug will be more potent
Effective Dose (ED50)
the dose at which the drug shows half of its maximal effect
How can we assess the relative potencies of 2 drugs?
by comparing their ED50 values, whichever drug has effects at lower doses is more potent than the other (whichever drug is left on the x-axis)
How can we compare drug efficacies?
by evaluating maximal responses rather than dose, whichever drug goes higher up on the y axis has a much greater maximal effect
Partial Agonist/Antagonist
a drug of only moderate efficacy
Phencyclidine
-PCP or Angel Dust
-NMDA receptor antagonist
-Mind-altering drug that may lead to hallucinations
-PCP is a non-competitive NMDA antagonist, while PCP is bound, no other ligand can activate the NMDA receptor
NMDA Antagonists
-Loss of responsiveness (not consciousness)
-Loss of sense of self/identity
-Dissociation
-Psychotic thoughts
-Sensory aberrations
-Aggression and agitation (rare)
-relation to Susannah’s psychosis
Another drug with similar effects to PCP
Ketamine (special K) – also a NMDA antagonist
Psychotomimetic
elicit psychotic symptoms in people
