Pharmacology of the Sympathetic Nervous System Flashcards
give a description of a sympathetic nerve
short preganglionic axons whose cell body located within the spinal cord in the intermediolateral column (IML) and long postganglionic axons
what is the main neurotransmitter released at sympathetic neuroeffector junctions
noradrenaline (along with ATP). there are also cotransmitters that are released such as NPY
what does sympathetic innervation of sweat glands release
acetylcholine (acts on muscarinic receptors)
what are the major agonists in the sympathetic system?
the catecholamines: noradrenaline adrenaline dopamine isoprenaline
describe beta-2 receptors
beta 2 receptors are not innervated and are inhibitory
decribe beta-1 receptors
beta 1 receptors are excitatory and innervated
what feature do all adrenoreceptors share?
they are all G-protein coupled receptor type receptors containing 7 transmembrane spanning domains
which effector mechanism is linked to alpha1 adrenoreceptors?
the alpha1 adrenoreceptors are primarily coupled to phospholipase C with an increase in IP3 and Diacylglycerol (DAG)
Which effector mechanism is linked to alpha2 adrenoreceptors?
negatively coupled to adenyl cyclase
Which effector mechanism are linked to beta adrenoreceptors?
increase in cyclic AMP and protein phosphorylation via protein kinase A
Where is noradrenaline primarily released from
sympathetic nerve terminals
where is adrenaline primarily released from
adrenal medulla
describe potency of noradrenaline
noradrenaline is more potent on alpha than beta
describe potency of adrenaline
adrenaline is more potent on beta than alpha
what is potency of isoprenaline
very selective for beta- adrenoreceptors
what are general alpha adrenoreceptor agonists and what are they primarily used for?
adrenaline and noradrenaline
primarily used for anaphylactic shock, cardiac arrest and to prolong anaesthesia
name an alpha1 agonist and what is it mainly used for?
phenylephrine
primarily used as a nasal decongestant
name an alpha2 agonist and what is it mainly used for?
clonidine
anti-hypertensive
name some other alpha2 agonists and what they are used for?
dipivefrine - adrenaline prodrug
bromindine
used to treat open angle glaucoma - reduces the rate of production of aqueous humour
what is the role of beta 2 selective agonists?
salbutamol and salmeterol
- used in asthma for bronchodilation and to relax the uterus in premature labour
what do indirect acting sympathomimetic drugs do?
release noradrenaline in the absence of nerve stimulation
name some indirectly acting sympathomimetics
tyramine
ephedrine
amphetamine
the effects of adrenaline on the heart are a combination of the actions of which two drugs?
noradrenalin and isoprenaline
beta1 agonists and what are they used for?
dobutamine and bisoprolol
used for congestive heart failure
