Adrenergic receptors

Adrenergic Rs:
-two family of receptor identified on the bases of there response to the adrenergic agonist (nor adrenaline , adrenaline , isoproterenol )
1) ? - adrenoceptor
Show weak response to synthetic agonist isoproterenol
Adrenaline ? nor adr >> isoproterenol
? 1:
specific agonist: phenylphrine
specific antagonist: prazosin
mech: G-pr Ip3 & DAG Ca++
located on most sm , vascular sm , eye , pilomotor sm , prostate capsule

the effect of ?-1 R:
- vasoconstriction ( especially skin and abdominal viscera but slight in cerebral and coronary) so increase total peripheral resistance and blood pressure
- mydriasis ( due to contraction of radial muscle of iris)
-increase closure of internal sphincter of bladder
-increase sweat gland secretion and piloerection
-male : ejaculation & contraction of prostatic capsule
-uterus : contraction
- intestinal sm : relaxation
-Metabolic effect : hyperkalemia

? 2:
specific agonist: clonidine
specific antagonist: yohimbine
mech: G-pr inhibit cAMP synthesis , increase K ,decrease Ca
located on presynaptic nerve ending , ?-cell of pancreas & sm of veins & git
also in lipocyte & in CNS decrease adrenaline release and hypotension.


? 2-effect:
-inhibit norepi release in cns leading to hypotension
-inhibit cholinergic and adrenergic neurotransmitter release
-platelet aggregation
-inhibit insuline release
-venous constriction & git sm relaxation
-inhibit lipolysis & rennin secretion





2) ?- adrenoceptor:
Isoproterenol > Adrenaline > nor adr

?-1:
affinity adr=nor adr
mech: G-pr stimulate cAMP synthesis
location: myocardium , kidney and fat cell

The effect of ?-1:
- tachycardia
-increase rate and force of contraction(inotropic and chronotropic)
-increase lipolysis
-increase rennin secretion by kidney

?-2:
affinity adr > nor adr
mech: G-pr stimulate cAMP synthesis
location :
sm of BV in sk m , bronchial tree , urinary bladder & uterus-
-liver
-?-cell of pancreas
-pump that shift K+into cell.

The effect of ?-2:
Vasodilatation in sk m leading to decrease peripheral resistance-
-bronchodilation
-relaxation of detrusor sm
-relaxation of uterine sm
-increase K uptake by sk m
-increase glycogenolysis in liver
-induce hypokalemia
-decrease release of autacoids

?-3:
Located on fat cell and activated lipolysis