Receptor& Substrates - common drug receptor targets Flashcards
agonist:
is a substance that binds to and activates a receptor, producing the same type of physiologic response as the endogenous substrate that binds to that same receptor.
biological effect (secretion of a hormone, contraction of a muscle, activation of an enzyme, depolarization of a membrane)
antagonist:
(sometimes called a _________________)
binds to a receptor but DOES NOT produce a subsequent reaction. The antagonist blocks the agonist from binding and inhibits the subsequent reaction.
blocker or inhibitor
The interaction of an antagonist with a receptor can be either ________________ or ___________
competitive inhibition
non-competitive inhibition
competitive inhibition:
the antagonist binds to the same active site of a receptor as the endogenous substrate
non-competitive inhibition:
is when the antagonist binds to the receptor at a site other than the active site (aka allosteric site), this causes the shape of the active site to change, so the endogenous substrate cannot bind to the active site on receptor.
example: so with epinephrine and albuterol
which one is endogenous?
what binding site do they both have in common?
epinephrine = endogenous, naturally produced by body
albuterol = exogenous substrate, produced outside of the body, functions as agonist
both bind to Beta-2 receptors and elicit same adrenergic biologic response
The endogenous neurotransmitter acetylcholine, primarily binds to ___________ or ________ receptors
Muscarinic receptors
Nicotinic receptors
When ACh binds to muscarinic receptors, what type of response is produced?
what are those symptoms
parasympathetic response —————— “rest and digest system”
SLUDD: increased activity of SLUDD
salivation/lacrimation/urination/defecation(diarrhea)/digestion(peristalsis)
SLUDD represents a syndrome of symptoms commonly referred to as _________________
cholinergic symptoms = SLUDD
When ACh binds to Nicotinic receptors, what symptoms occur?
increase in BP , HR
What are common drug muscarinic agonists AKA “cholinergic agonists”?
what symptoms occur
examples: pilocarpine, bethanechol,
they also increase SLUDD symptoms.
A reminder - cholinergic agonists will increase __________ symptoms.
example: pilocarpine - _______
SLUDD
can be given systemically to alleviate dry mouth associated with other conditions like shrogens disease. It does this by enhancing ACh activity. so increasing salivation, which in this cause is a desirable outcome. But of course, all the other components of SLUDD, may come along as side effects.
bethanechol
-used to treat urinary retention (condition in which you are unable to empty all the urine from bladder
increased urination from the cholinergic agonist is a desirable outcome, but again one may experience other side effects from SLUDD
Drugs that are antagonists to ACh are also called ________ and going to have the ____________ effect. Which is ________
anticholinergics
opposite
decrease SLUDD symptoms..
what are the anticholinergic side effects?
decrease salivation/lacrimation/urination/defecation/digestion
atropine
ACh antagonist.
-used to decrease salivation pre-operatively in patients who are going to receive anesthesia
-is an antidote for the chemotherapeutic agent irinotecan (Camptosar, Onivyde)
oxybutynin
is used for overactive bladder (symptoms of urgency & incontinence)
so decreasing urination with an antagonist
rocuronium
nicotine antagonist
-these drugs block the effects of ACh at those nicotinic receptors on skeletal muscle. Causing paralysis.
side effects would include decreased HR & BP
also other neuromuscular blockers
Remember: epinephrine and norepinephrine can act at multiple sites of ____________
adrenergic receptors
remember: alpha-1 adrenergic receptors are primarily located in the ______________.
Agonist activity at these receptors causes ______________ which __________
peripheral vascular smooth muscle
smooth muscle vasoconstriction, increases blood pressure
think of smooth muscle vasoconstriction as creating an increase in (SVR) systemic vascular resistance
Antagonist activity at alpha-1 adrenergic receptors causes _____________
alpha-2 adrenergic receptors are primarily located ________.
remember, with an excess of NE & EPi in the synaptic cleft, those NTs bind to the receptors on presynaptic neuron which ___________. With less of these NTs, it causes a
centrally in the brain on presynaptic neurons
signals a decrease in the release of NE & EPi is needed. - (we call this decrease in sympathetic output)
***“think of like a negative feedback loop”
with less NE and Epi being released this causes a decrease in BP and HR.
beta-1 adrenergic receptor are primarily located in the _________.
Agonist activity at these receptors causes ____________
heart
increased myocardial contractility, increased cardiac output, increased heart rate
beta-2 receptors are primarily located in the _________.
Agonist activity at these receptors causes _________
lungs
smooth muscle relaxation, dilation of bronchioles (bronchodilation)
