The Sympathetic Nervous System I and II

Question 1

What are post ganglionic sympathetic neurotransmitters?

Answer 1

noradrenaline, with ATP as a secondary transmitter. Co-transmitters can be NPY

Question 2

What is so special about sweat glands?

Answer 2

They release ACh post synaptically which acts on mAChRs.

Question 3

What G proteins are a-receptors coupled to and explain their mechanism

Answer 3

a1 receptors are coupled to Gq receptors. This is coupled with phospholipase C. When activated, PLC will cleave pip into DAG and IP3. IP3 will bind and release Ca2+, and this Ca2+ will work with DAG to activate PKC. PKC activation causes phosphorylation of the target protein.

a2 receptors are coupled with Gi proteins. This is an AC inhibitor on the pre-synpatic nerve terminal.

Question 4

What G proteins are B receptors coupled to and explain their mechanism.

Answer 4

Gs proteins - this is coupled with adenylate cyclase, which converts ATP into cAMP. cAMP will cause influx of Ca2+ and heart muscle contraction.

Question 5

Which B adrenoceptors are non-innervated?

Answer 5

B2 are non innervated and must rely on circulating adrenaline.

Question 6

What metabolic effects of skeletal muscle do B2 receptors mediate?

Answer 6

The conversion of glycogen into lactic acid, causing hyperlactic acidemia.

Question 7

What effect does a1 adrenoceptors have on the liver?

Answer 7

It will cause the release of K+, which leads to hyperkalaemia.

Question 8

What effect does a2 adrenoceptors have on insulin release

Answer 8

Activation of a2 adrenoceptors cause inhibition of insulin release.

Question 9

What is adrenaline reversal?

Answer 9

Adrenaline reversal occurs during the administration of a1 antagonists. When the a1 receptor is antagonised, the adrenaline will reveal effects on the B2 receptor, which is vasodilation and hence a fall in blood pressure.

Question 10

What is a adrenoceptor agonist used as a nasal decongestant?

Answer 10

phenylphrine

Question 11

What is a a-adrenoceptor antihypertensive?

Answer 11

clonidine

Question 12

What kind of drug is dipivefrine and what can it be used for? How does it work?

Answer 12

dipivefrine is used for simple open glaucoma >21 mmHg intraocular pressure. This is a prodrug. The esterification of adrenaline with pivalic acid will allow this drug to cross the cornea easily.

As a result, it will reduce the rate of production of aqueous humor by a2 activation and causing vasoconstriction of afferent arterioles in ciliary body. It also facilitates absorption of aqueous humor by activating a2 adrenoceptos on veins that drain the canal of schlemm.

Question 13

Why is dipivefrine contra-indicated in closed angle glaucoma?

Answer 13

Because the increase in pupillary size (mydriatic action) ill just worsen the angle.

Question 14

What can dobutamine be used for?

Answer 14

cardiogenic chock for cardiopulmonary resuscitation because it is a b1 agonist

Question 15

What are some side effects of salbutamol?

Answer 15

skeletal muscle tremors, hypokalemia

Question 16

What receptor agonists can be used in treatment of premature labour?

Answer 16

B2 to allow relaxation of uterine smooth muscle

Question 17

What are examples of indirect acting sympathomimetics?

Answer 17

Tyramine, Cocaine, Ephedrine, AMPHETAMINE

Question 18

What type of drug is phentolamine

Answer 18

Short acting reversible competitive alpha antagonist that is nonselective

Question 19

What type of drug is phenoxybenzamine?

Answer 19

Irreversible non competitive alpha antagonist that is non selective and non surmountable

Question 20

One use of Ergometrine

Answer 20

Postpartum haemorrhage

Question 21

One use of ergotamine

Answer 21

Migraine in acute attack

Question 22

One possible Ergot Alkaloid treatment for dementia

Answer 22

Hydergine

Question 23

Which B adrenoceptor antagonist shows local anaesthetic action?

Answer 23

Sotalol

Question 24

Which Beta blocker is used to treat aqueous humor production?

Answer 24

Timolol

Question 25

What can be an alternative option to surgery in the treatment of phaeochromocytoma?

Answer 25

a-methyltyrosine. This inhibits the tyrosine hydroxilase enzyme, causing block in the conversion of L tyrosine to L dopa. NA cannot be formed.

Question 26

What is the difference between MAO and COMT?

Answer 26

MAO and COMT both metabolize catecholamines, however COMT is specfic to catecholamines and MAO can metabolize other amines as well.

Question 27

Describe the Cheese Reaction

Answer 27

MAO usually metabolizes tyramine, which is present in foods made by bacteria in the intestinal epithelium. In the presence of MAO inhibition, the tyramine will enter via uptake 1 and displace NA. This evokes vasoconstriction at post junctional a adrenoceptors causing lethal hypertension. The likelihood of this phenomenon is reduced if mpatient is on a specific MAO-B inhibitor.

Question 28

What is the NA metabolite found in urine?

Answer 28

VMA. This is a good indicator of phaeocytochroma.