In 1948, Raymond Ahlquist published a manuscript in the American Journal of Physiology establishing the idea of adrenaline having distinct actions on both alpha and beta receptors.

[6][7] GPCRs play a key role in cell signaling pathways and are primarily known for their seven transmembrane (7TM) helices, which have a cylindrical structure and span the membrane.

[8] Upon the binding of a ligand to the extracellular domain of the GPCR, a conformational change is induced in the receptor that allows it to interact with the alpha-subunit of the G-protein.

Conversely, TnI phosphorylation results in its facilitated dissociation of calcium from troponin C (TnC) which speeds the muscle relaxation (positive lusitropy).

[16] One of the single nucleotide polymorphisms (SNPs) in ADRB-1 is the change from a cytosine to a guanine, resulting in a protein switch from arginine (389R) to glycine (389G) at the 389 codon position.

The receptor of the 49G variant is always expressed, which results in high coupling activity with adenylyl cyclase and increased sensitivity to agonists.

Additionally, patients with heart diseases that have a substitution of glycine for serine at codon 49 (49S > G) show improved cardiac functions and decreased mortality rate.

Healthy individuals with a glycine at codon 49 show better cardiovascular functions at rest and response to maximum heart rate during exercise, evident for the cardioprotection related to this polymorphism.

[18] Because ADRB-1 play such a critical role in maintaining blood pressure homeostasis and cardiac output, many medications treat these conditions by either potentiating or inhibiting the functions of the ADRB-1.

[19] It is also important to note the use of illicit drug for ADRB-1 since cocaine, beta-blocking agents, or other sympathetic stimulators may cause a medical emergency.