Sympathetic (Adrenergic) Pharmacology Flashcards
How does the PNS affect the GI glands, salivary glands, lacrimal glands, nasal glands?
The effect is from M3 muscarinic stimulation and produces watery secretory product
How does the SNS affect the GI glands, salivary glands, lacrimal glands, nasal glands?
The effect is from beta adrenergic stimulation and produces secretion of protein: enzyme and mucous
The effect alpha adrenergic stimulation and causes vasoconstriction, which decreases water and decreases and concentrates the secretion
How does the SNS affect vascular smooth muscle?
Causes contraction in the skin, splanchnic vessels via alpha1 receptors
Causes relaxation of the vessels in the skeletal muscle via muscarinic receptors
How does the PNS affect vascular smooth muscle?
It causes the release of EDRF form the endothelial cells via M3, which causes vessel relaxation
Norepinephrine mainly stimulates what receptors?
Alpha1 receptors in the vessels, which markedly increases blood pressure
Epinephrine mainly stimulates what receptors?
Epinephrine has a higher affinity for beta receptors (in cardiac muscles), which increases heart rate and contractility and has less effect on mean arterial pressure
How does the SNS affect GI smooth muscle?
The SNS relaxes the GI smooth muscle via beta2 receptors and causes contraction of the GI sphincter via alpha1 receptors
How does the PNS affect GI smooth muscle?
The PNS relaxes the GI sphincter and causes contraction of the GI smooth muscle via M3 receptors
What is denervation supersensitivity?
Destruction of sympathetic or parasympathetic nerves causes a decrease in function and there is a chemical adaptation of the organ, hence, an increase in intrinsic tone. There is also an increase in response to external neurotransmitter of organs that have been denervated due to an upregulation of cholinergic and adrenergic receptors in the end organs
What are adrenergic receptors?
There are at least 4 types: alpha1, alpha2, beta1 and beta2
Where do the adrenergic receptors work?
Effector organs: cardiac muscle, smooth muscle and glands. They all respond to norepinephrine and epinephrine (NE more to alpha and E more to beta)
What does the alpha1 receptor do? And what is the importance, medically?
Vasoconstriction (medical: nasal decongestant, increase BP in trauma/shock) Pupil dilation (medical: eye exams) Inhibits uterine contraction in pregnancy (medical: delay birth, side effect) Ejaculation (medical: none yet; drugs are in development) Contraction of bladder neck and prostate neck (medical: usually just a negative side effect)
What does alpha2 receptor do?
It is located in the presynaptic junction
It inhibits neurotransmitter release, thus inhibiting sympathetic (adrenergic) activation
What are the alpha2 responses?
Though it inhibits adrenergic activation, its not complete nor perfectly opposite of alpha1. For example, it causes cardiac (and other) vasoconstriction, decrease norepinephrine release in the brain and inhibits lipolysis and insulin release
What is the primary medical importance of alpha2?
It is in the CNS (neuronal) and in hypertension
What are the functions of beta1?
In the kidneys it causes the release of renin, which causes vasoconstriction
In the heart it increases heart rate, force of contraction and velocity of conduction in AV nodes
What are the functions of beta2?
Bronchial dilation Relaxation of uterine muscle Vasodilation Glycogenolysis Glucagon release
What does dopamine do?
Dilates renal blood vessels
What are the second messengers of adrenergic receptors?
Alpha1: IP3 and DAG
Alpha2: decrease cAMP
Beta1: increase cAMP
Beta2: increase cAMP
What is the distribution of adrenergic receptors?
Alpha1: blood vessels and GI spincters
Alpha2: presynaptic terminal
Beta1: heart
Beta2: airway, GI, urogenital
What are agonists of adrenergic receptors?
Alpha1: pseudoephedrine
Alpha2: clonidine
Beta1: isoproterenol and dobutamine
Beta2: Isoproterenol and terbutaline
What are antagonists of adrenergic receptors?
Alpha1: prazosin
Beta1 and beta2: propanolol
What are adrenergic agonists?
Stimulators (sympathomimetics) mimic the action of norepinephrine, dopamine and epinephrine
They can be selective or non-selective (of site, receptor subtype, tissue location)
Almost all are at least partially non-selective (majority of side effects)
How can adrenergic receptors be used?
Hemodynamic compromise (shock, depressed cardiac rhythm)
Bronchospasms (asthma)
Nasal and sinus congestion
Often used in emergency situations