adernergic agonists Flashcards
where can you find adrenergic receptors?
post synaptic in the sympathetic effector organs
or pre synaptic on the neuron
what are the steps of neurotransmission at the adrenergic neurons?
The process involves 5 steps: synthesis, storage, release, and receptor binding of norepinephrine, followed by removal
what are the two types of adrenergic receptors and how where they classified
alpha (a) and beta (b)
alpha has high affinity for epinephrine>norepinephrine>isoproterenol
beta has high affinity for isoproterenol>epinephrine>norepinephrine
where are alpha1 receptors located and what G protein do they activate
found on thr postsynaptic membrane if the effector organs.
they activate Gq protein—–> phospholipase C which increase IP3 and DAG
where are alpha 2 located and what result from their activation?
they are located on the sympathetic and parasympathetic presynaptic nerve endings.
they control the release of norepinephrine (inhibitory heteroreceptors) and acetylcholine (inhibitory heteroreceptors).
they work by GI protein—–inhibits adenylyl cyclase—–fall in cAMP levels.
MAO—-when norepinephrine binds to the alpha2 receptors it sends an inhibitory signal to stop the release of norepinephrine (auto inhibition) or acetylcholine (hetero inhibiton)
what are the further subdivisions of alpha receptors
alpha1—-a,b,c,d
alpha2—–a/b/c
what are the differences between beta1 and beta2 receptors
beta 2 has a higher affinity for epinephrine than norepinephrine while beta1 has the same affinity
what is the G protein for beta receptors
Gs proteins——-activates and increases adenylyl cyclase—–more cAMP
remember that
Adrenergically innervated organs and tissues tend to have a predominance of one type of receptor.
example: skeletal muscles have both a1 and B2 but B2 predominantes
Other tissues may have one type of receptor exclusively, like the heart which have B1 only
what does the simulation of ALPHA1 leads to
vasoconstriction
increased peripheral resistance
increased blood pressure
mydriasis (dilated pupils)
increased closure of internal sphincter of the bladder
what does alpha2 activation leads to
inhibition of norepinephrine and acetylcholine and insulin release
what does the activation of beta1 receptors lead to
tachycardia
increased lipolysis
increased heart contractility
increased release of renin
what does the activation of beta2 lead to
vasodilation
decreased peripheral resistance
bronchodilation
increased glycogenolysis
increased glucagon
relaxed uterine smooth muscle
what are the three mechanisms that explains the desensitization of adrenergic receptors
1) sequestration of the receptors so that they are unavailable for interaction with the ligand
2) down-regulation, that is, a disappearance of the receptors either by destruction or by decreased synthesis
3) an inability to couple to G-protein, because the receptor has been phosphorylated on the cytoplasmic side.
what do adrenergic agonists look like and what are the important structural features
they look like b-phenylethylamine derivatives
•1) the number and location of OH substitutions on
the benzene ring
•2) the nature of the substituent on the amino
nitrogen.