Adrenergic Receptors: β Subtype

β adrenergic receptors or β-adrenoceptors show a stronger response to ISO, compared to Adr and NA.

Upon stimulation, all β-adrenoceptors activate adenylyl cyclase leading to increased cAMP production and modulation of calcium channels.

These receptors are further classified into three subtypes based on various factors.

β₁ receptors have almost equal affinity for both Adr and NA. They are located predominantly in cardiac tissue, lipocytes, and renal cells.

Their stimulation causes tachycardia, lipolysis, and renin production.

β₂ receptors have a higher affinity for Adr than NA. They are located postsynaptically in the smooth muscles of the cardiovascular, respiratory, and genitourinary systems. They are responsible for causing bronchodilation, vasodilation, decreased peripheral resistance, relaxation of the bladder and gravid uterus.

β₃ receptors show higher sensitivity to NA than Adr. They are located postsynaptically on the lipocytes and bladder. They regulate metabolic activity and lipolysis, and relax the bladder's detrusor muscle.