Lecture 6 Flashcards
metabotropic receptors steps
1- neurotransmitter binds g protein coupled receptor
2- G protein activated, G protein subunit moves to adjacent ion channels, causes a brief delay, may also trigger second messenger systems
3- channel opens, ion flows across membrane for a longer period of time
kinases
phosphorylates (add phosphate group)
phosphorylation is actively reversed by
phosphotase
why have metabotropic receptors?
because they act as synaptic modulators
actions are slower than ligand gated, but last a lot longer
can act beyond synapses on ion channels and other molecules
NE, E, DA, and seratonin act primarily on what receptor
metobotropic
agonist
substances that bind to and activate the receptor
can be endogenous or exogenous
antagonists
substances that bind to the receptor but do not activate it (blockers)
noncompetitive antagonists
binds to a different site than the neurotransmitter and prevents neurotransmitter from having an effect
competitive antagonist
binds on the same place as NT but doesn’t activate it or let the NT bind
partial agonists
activate the receptor but not as well as the endogenous agonists
affinity
how well does the drug or NT bind to the receptor
efficacy
how well does the drug or NT activate the receptor after it is bound
low affinity
binds on but releases quickly
potency
how much of the drug is needed to get an effect (ED50)
ED50
half the maximal response
higher potency
if it takes a lower dose to reach ED50 then it is more potent
higher efficacy
a higher response to the same dose is a higher efficacy
therapeutic index
how big is the difference between the effective and lethal dose
LD50
half the subjects die
repeated exposure of a drug can lead to
metabolic tolerance
functional tolerance (up regulation of receptors (antagonist) down regulation of receptors (agonists) and withdrawal)
sensitization
what happens if the ED50 shifts to the right but the LD50 doesn’t change
you need more and more of drug to reach euphoria but it takes you closer and closer to lethal dose
upregulation of receptors
if a drug antagonizes (inhibits) a receptor, they need more receptors to get the same effect since some are now blocked
