Veterinary Neuropharmacology

CATECHOLAMINES

• 3, 4, dihydroxybenzene is called catechol and hence the drugs that have this structure are called catecholamines.

• Epinephrine, norepinephrine and dopamine are known as endogenous catecholamines.
• Isoproterenol is a synthetic catecholamine.
• Epinephrine (EPI), norepinephrine (NE) and isproterenol exhibit varying agonistic actions on the adrenoceptors.
• The effect of alpha adrenergic action of catechoamines ( contraction of smooth muscle )is in the order of : EPI ≥ NE >> ISO
• and the beta adrenergic effect (relaxation of smooth muscle ) is in the order of : ISO > EPI

Effects of catecholamines

	NE	EPI	ISO
Alpha effects	Potent alpha stimulant (usually less than EPI)	Most potent alpha stimulant	least potent
Beta effects	Weak stimulant of blood vessel β2 receptor	Potent β stimulant	Most potent β stimulant
	Weak to moderate stimulant of smooth muscle β2 receptor outside the blood vessels
	Potent stimulant of heart (β1 stimulant )