Drugs and Their Receptors

Question 1

What are the types and effects of adrenergic receptors?

Answer 1

Stimulate alpha-1 and beta-1 receptors.
Inhibit alpha-2 and beta-2 receptors.

Question 2

What do alpha-1 receptors work on?

Answer 2

Alpha 1 receptors are adrenergic receptors.
GQ protein coupled to produce stimulatory effect
Found in:
- blood vessels –> Vasoconstriction
Certain smooth muscles of urogenital tract –> contraction e.g. oppose voiding bladder and ejactulation.
- glands –> secretion
- GI tract –> relaxation

Agonist: phenylephrine
Antagonist: prazosin

Question 3

What do beta-1 receptors work on?

Answer 3

Found in:
- Heart
SA note –> increase rhythmicity increase heart rate
AV node –> increase conduction velocity
ventricular myocytes –> increase contractility
- Juxtaglomerular cells in kidneys –> increase renin release

Selective agonist: Dobutamine
Selective antagonist: metoprolol, atenolol, etc

Question 4

What do Beta 2 receptors act on?

Answer 4

Found in:
Bronchi –> Bronchodilation
Blood Vessels –> vasodilation
uterus –> relaxation
GI tract –> relaxation
Pancreas –> glucagon secretion
Eye –> increase aqueous secretion
Detrusor muscle –> relaxation

Selective agonist: Salbutamol, terbutaline
Selective antagonist: alpha-methyl propanolol

Question 5

What do beta 3 receptors act on?

Answer 5

Found in adipose tissue and detrusor muscle to cause relaxation
Selective agonist: mirabegron

Question 6

What are the effects of the dopamine and its receptors when stimulated?

Answer 6

Dopamine is a catecholamine that has mixed adrenergic effects.
It has little alpha-adrenergic effects

lower doses (0.5-3mcg/kg/min): Dilate renal mesenteric coronary vascular beds. Useful in oliguric renal failure.

higher doses (5-13 mcg/kg/min): has beta-1 adrenergic agonist affects resulting in vasodilation. Can be used to improve cardiac output by decreasing afterload.

Dose range: 1-20mcg/kg/min. Discontinue if tachycardic or arrhythmic.

Question 7

What are the effects of norepinephrine?

Answer 7

Norepinephrine is a mixed adrenergic agonist with a stronger effect on alpha-1 receptors than beta receptors.

It causes increased vasoconstriction.
It will commonly lower heart rate on account of baroreceptor reflex with increased blood pressure
Caution: Large dose of norepinephrine can cause profound bradycardia

Concern: to much vasoconstriction increases afterload causing decreased cardiac output.

Dose: 0.1 - 2mcg/kg/min

Question 8

What are the effects of phenylephrine?

Answer 8

Phenylephrine is an alpha-1 agonist.
Indicated for hypotension when beta-adrenergic agonist effects are not desirable.
Can cause increased blood pressure and bradycardia.
too much vasoconstriction can increase afterload and decrease output. (Use with caution in patient with bradycardia or cardiac disease).

Dose: 0.1-2mcg/kg/min

Question 9

What are the effects of vasopressin?

Answer 9

Vasopressin is also known as anti-diuretic hormone.

It causes vasoconstriction independent of adrenergic stimulation.
It is commonly used in conjunction with norepinephrine for refractory hypotension.
Vasopressin is not affected by pH making it ideal for use during prolonged CPR.

Dose: 0.01-0.04units/kg/min
Strength: 0.01units/ml

Question 10

What are the effects of epinephrine?

Answer 10

Epinephrine is a mixed adrenergic agonist with both alpha 1 and beta one agonist properties

Low dose: beta-adrenergic effects predominate improving cardiac output and cardiac contractility

higher doses: more of an alpha-1 adrenergic agonist resulting in vasoconstriction.

CRI dose: 0.1-2.0mcg/kg/min

Question 11

What do alpha-2 receptors work on?

Answer 11

Gi/Go coupled proteins acting on adenylyl cyclase cAMP pathway to produce inhibitory effects

receptors located prejunctional in nerve endings to inhibit transmitter release
Receptors in the brain decrease sympathetic flow
receptors in the pancreatic beta cells inhibit the release of insulin
Alpha 2 promotes platelet aggregation
receptors in the blood vessels induces vasoconstriction

Agonist: Clonidine
Antagonist: Yohimbine

Question 12

Cholinergic Muscarinic receptors

Answer 12

Involved in peristalsis, micturition, bronchoconstriction and several other parasympathetic reactions.

Muscarinic receptors are type of ligand-gated G-protein coupled receptor and are linked to second messenger systems.

Muscarinic receptor varies with the receptor subtype.

These receptors occur in the CNS and the autonomic parasympathetic division of the PNS.

Question 13

Cholinergic receptors

Answer 13

Two types of cholinergic receptors: Nicotinic and muscarinic

Question 14

Cholinergic nicotinic receptors

Answer 14

Found on skeletal muscles in the autonomic division of the peripheral nervous system and in the central nervous system.

Nicotinic receptors are monovalent cation channels through which both sodium and potassium can pass.

Question 15

Adrenergic receptors

Answer 15

Are divided into two classes (alpha and beta) with multiple subtypes each.

Adrenergic receptors are linked to G proteins and initiate a second messenger cascade.

Question 16

Glutaminergic Receptors

Answer 16

Metabotropic glutaminergic receptors act through G-protein-coupled receptors. Two types of glutaminergic receptors are receptor channels.

Question 17

Glutamate

Answer 17

The main excitatory neurotransmitter in the CNS and also acts as a neuromodulator.

Action of glutamate at a particular synapse depends on which of its receptor types occurs on the target cell

Question 18

alpha amino-3-hydroxy-5 methylisoxazole-4-proprionic acid)

AMPA receptors

Answer 18

Ligand-gated monovalent cation channels are similar to nicotinic acetylcholine channels.

Glutamate binding opens the channel, and the cell depolarizes due to net sodium influx.

Question 19

N-methyl-D-aspartate

NMDA receptors

Answer 19

cation channels that allow sodium, potassium, and calcium to pass through the channel

Channel opening requires both glutamate binding and a change in membrane potential.

NMDA receptor channel is blocked by magnesium ions at resting membrane potentials.

Glutamate binding opens the ligand-activated gate, but ions cannot flow past the magnesium. If the cell depolarizes, the magnesium blocking the channel is expelled, and ions flow through the pores.

Question 20

Gamma-aminobutyric acid type A (GABA A)

Answer 20

Ligand-gated ion channels that allow chloride ions to pass into cells.

Look into this answer more.

Question 21

muscarinic

Question 22

serotonin