Pharmacology - Autonomic Drugs Flashcards
which part of the nervous system makes no synaptic junction in (ganglia) betw the spinal cord and effector organ?
somatic (voluntary) nervous system
are the nerves of the somatic nervous system myelinated?
yes
if you section the somatic nn, what happens?
muscle paralysis, resulting in muscular atrophy
*somatic nn regenerate very slowly
which part of the nervous system makes synaptic junction in (ganglia) betw the spinal cord and effector organ?
autonomic nervous system
are autonomic nn myelinated?
preganglionic fibers are myelinated; postganglionic fibers are not.
In the parasympathetic nervous system, where does the cranial outflow originate?
CN’s III, VII, IX, & X
In the parasympathetic nervous system, where does the sacral outflow originate?
sacral nn = 2, 3, 4
Which part of the autonomic nervous system has more preganglionic nn? which one has more postganglionic nn?
more preganglionic to postganglionic nn = parasympathetic sys
more postganglionic to preganglionic = sympathetic sys
Where do the SNS’s preganglionic nerve fibers originate?
lateral horns of spinal cord (T2 to L2 or L3)
What type of innervation does the bronchi have? What about bronchial smooth muscles?
bronchi = sympathetic; bronchial SM = parasympathetic
What would happen if you sectioned autonomic nns?
does not completely abolish function of organ bc most of the organs have intrinsic functions
What NT does the somatic nerv sys use? And what is the effector organ?
AcH; skeletal muscle (motor)
What are the NTs for sympathetic inn to the smooth muscles, cardiac cells, and gland cells? Include pre-/postganglionic.
preganglionic = Ach postganglionic = NE
What are the NTs for sympathetic inn to the sweat glands? Include pre-/postganglionic.
preganglionic = Ach postganglionic = Ach
What are the NTs for sympathetic inn to the adrenal gland’s medulla ganglion? Include pre-/postganglionic.
preganglionic = Ach postganglionic = cells of the medulla which secrete epi/NE
How do the postganglionic cells of the adrenal medulla secrete epi/NE?
directly into the blood stream rather than into a synapse
What role does NE have in the brain?
for arousal
What role does dopamine have in the brain?
motor coordination, pleasure
What role does serotonin have in the brain?
appetite, depression
What role does glycine have in the CNS?
inhibitory NT in the spinal cord
What role does GABA have in the CNS?
suppresses activity of neurons in CNS
What is anandamide?
endogenous cpd similar to marijuana that has anti-anxiety effects and related to bliss or delight
what are enkaphalins?
endogenous opioids for suppressing pain
All of the inner linings of blood vessels in the periphery (endothelial cells) produce what continuously? And what type of nerves supply this?
NO; adrenergic
What does NO do?
opposes the excitatory actions of blood vessels (vasodilation, inc blood flow); in smooth muscle it will cause hypotension
What are the events occurring during an erection involving NO and NE?
NE is released in blood vessels all the time, but when NO is released during erection, its effect overpower the vasoconstriction caused by NE until ejaculation. Then the NE overpowers the NO lowering the blood flow.
What molecule does NO activate during an erection?
activates soluble guanylate cyclase
what does guanylate cyclase do?
synthesizes cGMP from GTP
_____ is believed to be the main vasoactive nonadrenergic, noncholinergic neurotransmitter and chemical mediator of penile erection
Nitric oxide (NO)
Acting as a second messenger molecule, ____ regulates the activity of calcium channels as well as intracellular contractile proteins that affect the relaxation of corpus cavernosum smooth muscle
cGMP
What are some excitatory NTs?
dopamine, NE, epi, glutamate, acetylcholine
What are some inhibitory NTs?
serotonin, GABA, anandamide (this last one could also have excitatory effects–not sure yet)
____ has an important role in cognition and memory. (Think Alzheimer’s.) Also in motor movements. (Think Parkinson’s.)
Ach
What is released from terminals of specific sensory neurons and associated w/ inflamm and pain?
Substance P!
- it coexists w/ excitatory NT glutamate in primary afferents that respond to painful stimul.
- may be involved in neurogenic inflamm
what types of fibers/nerves are cholinergic?
- pregang fibers of both sympathetic & parasympathetic nerv sys
- postgang PS fibers
- post gang sympathetic n for sweat gland
- pregang sympathetic fibers to adrenal gland
- somatic nn
what types of fibers/nerves are adrenergic?
postgang fibers of sympathetic sys (except for those innervating sweat glands–cholinergic nn)
*also adrenal medulla are modified sympathetic neurons that release epi/NE
what types of fibers/nerves are nitrergic?
postgang fibers innervating sex organs, some postgang fibers in intestine & lower esophageal sphincter
What effect does NE have on the heart? On the brain? On the eyes? In the intestine?
heart - inc HR, force, BP
brain - inc signals (inc alertness)
eyes - dilates pupil
intestine - inc sphincter tone (contracts) & relaxes mm–can cause constipation
*recall that NE is released during postgang sympathetics (w/ the exception of sweat glands & adrenal medulla)
what is Ach’s effect on the sphincter?
Ach relaxes sphincter.
how much NE is taken back up in the synaptic cleft?
80-90%; the majority!
*process called neuronal uptake
Small fraction of NE in the cytosol is metabolized by what?
MAO–monoamine oxidase
Some of the NE is taken up by extraneuronal cells and metabolized by?
COMT
Epi & NE are synthesized from what AA?
tyrosine
How is tyrosine converted to DOPA? And then how is DOPA converted to dopamine?
- Tyrosine to DOPA via tyrosine hydroxylase
- DOPA to dopamine via L-DOPA decarboxylase (aka L-aromatic AA decarboxylase aka LAAD)
How is NE made from dopamine?
chromogranins (aka Dopamine-B-hydroxylase)
What ion influx triggers exocytosis of NE into the synaptic cleft?
Calcium
What enzyme converts NE to epi?
PNMT = phenylethanolamine N-methyltransferase
What are differences between NE & epi?
- NE = NT; acts locally—is released from the nn.
- Epi = hormone; can act at a distance (circulates, acts on many tissues)
What is a neuromodulator and an example of a neuromodulator?
- substance that can enhance/reduce release of NTs; ex. angiotensin 2
Metyrosine is used to treat what disease?
pheochromocytoma (tumor of adrenal gland)–secrete high amts of catecholamines
what is the rate limiting step of NE synthesis?
tyrosine hydroxylase step; used in tx for pheochromacytoma (drug: Metyrosine)
Issues w/ DOPA decarboxylase results in…? What is the tx for this?
degeneration of neurons in brain that release DOPA; L-DOPA or carbidopa
What is carbidopa used for?
Tx for Parkinson’s; used in adjunct w/ L-DOPA
- carbidopa does NOT cross the blood-brain barrier, so it works in the periphery (reduces metabolism of L-DOPA in periphery)
- L-DOPA is in the periphery, but is not blocked completely in the brain–so it is more available there, if we reduced its metabolism in the periphery.
What is the main goal of the tx for parkinson’s?
inc production of dopamine!
- this is done by increasing levels of DOPA by using L-DOPA & carbidopa.
- reduce DOPA metabolism in the periphery (you want more of it in the brain!)
Disulfiram is used to treat what?
alcoholism; inhibits actylaldehyde dehydrogenase; disulfiram chelates w/ Cu in dopamine-B-hydroxylase (enzyme that converts dopamine to NE), inhibiting it!
- you will accumulate acetylaldehyde if you use this drug… so if you drink and take this drug, you may get hypertension!!
What effect does excess acetylaldehyde cause?
flushing, headache, nausea, vomiting, perfuse sweating
vesicular monoamine transport system (VMAT)?
transport NE and dopamine into synaptic vesicles; H out and NE in
What is reserpine? Tx for?
- an inhibitor of DA & NE uptake into synaptic vesicles (blocks VMAT)
- inhibits NE production bc blocked entry of dopamine into the vesicle
- also no storage of NE (depletes NE from nn)
- tx for hypertension & psychosis; to reduce agitation in horses
- does NOT interfere w/ uptake from nerve memb–only the vesicles!!
What is reserpine’s effect in the brain?
depletes dopamine, NE, serotonin
*when they began to use reserpine to treat hypertension & psychosis, pts began to show suicidal tendencies.
What does the PSNS do to the GI system?
promotes peristalsis and gut motility
What nerv system causes GI cramps & diarrhea?
dec in NE (dec in SNS); inc in PSNS
what converts a-methyldopa to a-methyldopamine?
dopadecarboxylase
what converts a-methyldopamine to a-methylNE?
dopamine-B-hydroxylase
What is a-methyldopa (aldornet) used for?
pregnancy induced hypertension (preecalampsia)
a-methylNE is taken up by the nerves and…?
displaces NE (“false NT” bc it is not an endogenous substance but stored and acts like NE); activates alpha-2-receptors and reduces the flow of impulses from the brain
- it dec sympathetic activity > leads to dec in flow of impulses > dec NE release
MAIN PT: a-MNE lowers BP
Pre-junctional/Pre-synaptic actions of a drug acts on the _______.
nerve terminal
What is Bretylium Tosylate?
an IV or IM injection that inhibits NE release and is used in intensive care or coronary care units for life threatening ventricular arrhythmias.
How does Bretylium Tosylate work?
- It increases ventricular fibrillation threshold.
- produces initial transient inc followed by inhibition of NE release
- increases action potential duration & effective refractory period
- it basically dec the output of the SNS in the periphery
What happens when you take cocaine in the body?
- cocaine blocks the reuptake of NE at varicosity memb
- NE will accumulate = more energetic, higher BP/HR/etc
- in the brain - also inhibits uptake of dopamine & serotonin
which agent will not be able to alter blood pressure after taking cocaine?
amphetamine
*must know that this occurs when you take cocaine before MAO or amphetamine due to the transport pump being blocked.
how can cocaine cause a cardiac arrest?
blocks Na conduction in the heart due to its local anesthetic effect
The amine pump on the varicosity memb can take up what substances?
NE, epi, DA, & indirect sympathetic amines (amphetamine, tyramine)
What is the diff betw the 2 indirect sympathetic amines?
Tyramine is metabolized by MAO in the GI tract, but
amphetamine is not.
*if you take an inhibitor of MAO, you will inc tyramine and thus inc NE release from nerves.
What is the main action of amphetamine and tyramine?
They get into the nerve and pumps NE out of the nn. Indirectly, cause inc in HR, BP, etc.
What metabolizes extraneuronal uptake of catecholamines? What inhibits this?
metabolized by MAO & COMT; inhibited by corticosterone
What drugs block neuronal uptake of NE into nn?
cocaine, tricyclic antidepressants (desipramine)