Ch. 8: Intro to Autonomic Drugs Flashcards
Pharmacology
the study of histories, sources, chemical properties, biological actions, biological handling and therapeutic uses of drugs in living organisms
main fxs of ANS (3)
- maintains homeostasis of visceral tissues
- regulates the functions of 3 primary cell types: smooth m, cardiac m, and secretory glands
- provides a means for the body to alter the functions of many tissues in response to external or internal changes (i.e. senses, body temp, pain, BP, fear, dz)
pharmacotherapeutic uses of autonomic drugs (3)
- re-establish “normal” function in dysfunctional organs (i.e. CV, GI, resp., urinary tract, etc. disorders)
- offset visceral changes secondary to CNS disorders or treatment with CNS-acting drugs
- treat poisonings and hypersensitivity reactions
classification of phenylephrine
alpha-1 adrenergic agonist
What are the effects of phenylephrine administration**
(alpha-1 agonist)
- vasoconstriction
- increase BP
- increase total peripheral resistance
- DECREASE in heart rate
Why does phenylephrine cause DECREASE in heart rate?**
Vasoconstriction/Increased BP activates baroreceptors/stretch receptors, which results in reflex arc from receptors –> CNS –> cardiac output/HR falls to try to compensate for increased BP
Integration centers at brainstem or above control which functions?
baroreceptor, GI secretion, sweating
Integration centers on spinal cord control which functions?
vasomotor tone
bladder emptying
defecation
GI motility
main fx of afferent nerves
relay status of heart/lungs/kidney/vascular stability back to CNS where it is processed/integrated
Drugs we use primarily target where on autonomic reflex circuit?
postganglionic nerves (for both sympathetic and parasympathetic)
Ach primarily acts on which type of receptors?
nicotinic ganglionic receptors
What type of drugs target integration centers (forebrain, brainstem, etc.)
tranquilizers, sedatives, anesthetics, stimulants
What type of drugs target autonomic ganglion?
nicotinic (i.e. nicotinic cholinergic antagonist) and anti-AChE drugs
What type of drugs target neuroeffector junction?
adrenergic, cholinergic, and anti-AChE drugs
Why do we rarely target autonomic ganglion?
because all the ganglia utilize a similar primary mech. of neurotransmission utilizing ACh acting on nicotinic receptors
Primary intended site of action for ANS drugs***
neuroeffector junction
T/F: nearly all visceral tissue receive dual innervation by sympathetic and parasympathetic neurons
T
T/F: neuroeffector junctions are located at many sites throughout the body
T
pharmacological antagonism
blockade of an agonist by an atagonist
physiological antagonism
opposing actions produced by two drugs via actions on different receptors or via distinct mechs.
How does atenolol work?
blocks EP at cardiac beta-1 receptors
Histamine causes constriction/dilation of bronchiole smooth muscle?
constriction
What causes dilation of bronchiole smooth muscle? via what receptors?
epinephrine on beta-2 adrenergic receptors
Advantages of physiological antagonism
- allows for different pharm. approaches for management of numerous disorders
- allows for complimentary txs that target branches of the ANS (ie. to speed up HR, you can either block parasympathetics, or stimulate sympathetics)
does isoproterenol stimulate or block sympathetic input to heart?
stimulate
does atropine stimulate or block parasympathetic input to heart?
block. Thereby stimulating heart
Sympathetic postganglionic neurons utilize what NT? What receptors do they act on? **
NE and EP. Act on alpha-1/2 and beta-1/2 adrenergic receptors
Parasympathetic postganglionic neurons utilize what NT? What receptors do they act on?
Ach. Act on muscarinic receptors
Sites of drug action in parasympathetic neurons**
Ach synthesis Ach release presynaptic receptors postsynaptic receptors*** Ach elimination (AchE)***
Sites of drug action in sympathetic neurons**
NE biosynthesis NE storage and release (from vesicles) presynaptic receptors*** postsynaptic receptors*** NE and EP elimination***
Preganglionic neurons use what NT for parasympathetic side? Sympathetic side?***
ACh for both!
Preganglionic neurons use what receptor types for parasympathetic side? Sympathetic side?***
Nicotinic for both!
Postganglionic neurons use what transmitter for para. side? Sym. side?***
Para: Ach
Sym.: NE and EP
Postganglionic neurons use what receptor type for para. side? Sym. side?
Para: muscarinic
Sym: alpha-1,2 beta-1,2
T/F: There is NO uptake (transport) process for Ach elimination in parasympathetic neurons***
TRUE. Ach elimination is via AChE only!
how does botulinum toxin work?
inhibits Ach release in motor neurons
Name 3 drugs that act on postsynaptic receptors in parasympathetic neurons, either as agonists or antagonists**
bethanechol (agonist of AchE)
atropine, glycopyrrolate (antagonists of AchE)
Name 3 drugs that act on Ach elimination (via AchE) in parasympathetic neurons**
edrophonium
physostigmine
parathion
major target for therapeutic control of parasymp. function**
postsynaptic receptors
On sympathetic side, drugs primarily target receptors pre/postsynaptically
postsynaptically
How do drugs act on presynaptic receptors on sympathetic neurons?
increase or decrease NT release from nerve terminals
major target for drug action on sympathetic neurons
postsynaptic (alpha or beta) receptors
In sympathetic neurons, how is NT (EP or NE) eliminated?**
2 ways:
1) uptake (most important; inhibited by ketamine)
2) enzymatic degradation (via multiple enzymes, such as MAO)
