Adrenergic drugs are basically sympathomimetic drugs.
They act on adrenergic receptors i.e beta 1,beta 2,beta 3 and on Alpha 1 receptor.Adrenergic drugs have same action as of adrenaline or nor adrenaline but the difference is that adrenergic drugs are synthetic so they will have some adverse effects as well,also some adrenergic drugs acts on some receptor more effectively and less effectively on other receptors.
To understand the action of adrenergic drugs we need to understand about the receptors on which they acts and where are these receptors present, also what happens when these drugs or adrenaline or nor adrenaline acts on these receptors.To answer all these questions let us start and move ahead.
Keep in mind that
•Nor adrenaline acts on Alpha 1 and beta 1 receptors only
•Adrenaline can act on any Alpha 1,beta 1,beta 2,beta 3 receptors
Effect of Adrenergic Drugs-
1)On Heart:-Beta 1 receptor is present on heart when these drugs acts on this receptor than FOC,CO,HR is increased which causes increase in BP.
2)On Blood vessels:- Alpha 1 receptor is present on blood vessels when drugs acts then it causes vasoconstriction which causes increase in BP Also beta 2 receptor is present on it when drugs act it causes vasodilation and so BP dec. to normal.
3)On Bronchus:- Beta 2 receptor present on Bronchus dilates when adrenergic drugs act on them.
4)On Liver:- Beta 2 receptor present in liver causes gluconeogenesis and glycogenolysis.
5)Fatcells:- Beta 3 receptor present on fat cells when these drugs acts on them it causes lipolysis and calorigenesis.
6)GIT:- Alpha 1 and Beta 2 receptor both are present in GIT it causes relaxation of GIT and decreased peristaltic movement.
7)Urinarybladder:-Beta 2 receptor is present on detrussor muscle when drug acts on it then bladder relaxes.Alpha 1 receptor is present on internal sphincter when drug acts on then it contracts and is closed.
8)Uterus:- Beta 2 receptor is present in uterus when drugs act it is relaxed.Alpha 1 receptor present on uterus when drug given it causes contraction of uterus.Like after pregnancy to bring back the normal size of uterus the drugs are given which acts on these receptor and causes uterine contraction.
9)Eye:- Beta 2 receptor present on ciliray epihelium of eye when drug acts here then aqueous humour is increased.Alpha 1 receptor on blood vessels of choroid when drug acts on it then these blood vessels contract causing decrease in aqueous humor.Alpha 1 receptor is also present on iris when drug acts here it causes dilation of pupil (mydriasis).
10)Diaphragm:- Beta 2 receptor present on it when drug acts here it causes increase in activity of diaphragm.
11)Beta cells of Pancreas:- Beta 2 receptor present here when drugs act then insulin release is stopped which causes hyperglycemia.
12)Neuro muscular junction:-Beta 2 receptor is present here when drugs act it causes increase in muscle power
Now to summarise:-
•Beta 1 receptor present on – Heart
•Beta 2 receptor present on – Bronchus, Liver, Ciliary epithelium of eye, Uterus, Detrussor muscle of urinary bladder, GIT, Blood vessel , Beta cells of pancreas , Diaphragm, Muscles (NMJ)
•Beta 3 receptor present on – Fat cells
•Alpha 1 receptor present on – Blood vessels,Internal sphincter of bladder,Uterus,GIT,Iris
Nor adrenaline acts on brain and causes decrease in Appetite.
Serotonin acts on brain and induces satiety.So,the drugs which acts similarly to them can be used as anti obesity drugs.Will be talking more about anti obesity drugs in upcoming posts.
Contributor- Medico Anant Singh Nanda
