Veterinary Neuropharmacology

Subtypes of adrenoceptors

ALPHA RECEPTOR SUB TYPES

	a 1	a 2
Location	Postjunctional effector organs	Prejunctional nerve ending, postjunctional in brain, pancreatic β cells, platelets and extrajunctional in blood vessels
Function subserved	Smooth muscle – contraction Blood vessels -Vasoconstriction Glands – decreased secretion Gut – relaxation Heart – arrhythmia	Inhibitors of transmitter release Blood vessels-Vasoconstriction Decreased central sympathetic flow Decreased insulin release Platelet aggregation
Selective agonist	Phenylephrine, methoxamine	Clonidine
Selective antagonist	Prazosin	Yohimbine

BETA RECEPTOR SUB TYPES

	β1	β2	β3
Location and function subserved	Heart – increased heart rate, increased force of contraction, increased AV nodal conduction velocity Juxtaglomerular cells in kidney – increased renin secretion	Bronchi – relaxation Blood vessels – Vasodilatation Uterus – relaxation GI tract – relaxation Urinary tract – relaxation Skeletal muscle – glycogenolysis Liver – glycogenolysis	Adipose tissue - lipolysis
Selective agonist	Dobutamine	Salbutamol
Selective antagonist	Atenolol	Butoxamine