[1] To avoid confusion, naming was continued with the letter D. Catecholamines like norepinephrine (noradrenaline) and epinephrine (adrenaline) signal through the α1-adrenergic receptors in the central and peripheral nervous systems.
Blood vessels with α1-adrenergic receptors are present in the skin, the sphincters[4] of gastrointestinal system, kidney (renal artery)[5] and brain.
Other effects on smooth muscle are contraction in: Activation of α1-adrenergic receptors produces anorexia and partially mediates the efficacy of appetite suppressants like phenylpropanolamine and amphetamine in the treatment of obesity.
While DAG stays near the membrane, IP3 diffuses into the cytosol and to find the IP3 receptor on the endoplasmic reticulum, triggering calcium release from the stores.
[18] In contrast to α2-adrenergic receptors, α1-adrenergic-receptors in the arterial vasculature of skeletal muscle are more resistant to inhibition, and attenuation of α1-adrenergic-receptor-mediated vasoconstriction only occurs during heavy exercise.
This action is generally undesirable in such agents and mediates side effects like orthostatic hypotension, and headaches due to excessive vasodilation.