By 
Ipamorelin binds the ghrelin receptor, designated GHS-R1a, with high selectivity that distinguishes its receptor engagement profile from earlier growth hormone-releasing peptides, including GHRP-6 and GHRP-2, at compatible operators. Ipamorelin’s selectivity at compatible operators limits co-secretion events involving cortisol and prolactin that less selective ghrelin receptor agonists produce at comparable receptor occupancy levels at compatible operators. Understanding how Ipamorelin’s receptor binding profile differs from other growth hormone-releasing peptides provides a mechanistic context for research that isolates GH pathway effects from adrenocorticotropic and prolactin co-secretion variables at compatible operators.
Ipamorelin receptor binding profile
The ghrelin receptor GHS-R1a is a highly selective receptor for ipamorelin. Because this growth hormone secretagogue does not induce the co-secretion of cortisol or prolactin, unlike older growth hormone secretagogues, like GHRP-6 and GHRP-2, which induce these hormones by binding less selectively at less compatible receptors, this growth hormone secretagogue does not induce the co-secretion of cortisol or prolactin. A low selectivity profile at compatible operators allows Ipamorelin to be clearly distinguished from first-generation growth hormone-releasing peptides.
The GHS-R1a receptor at compatible operators is a class A G protein-coupled receptor that signals through Gq protein coupling to activate phospholipase C at compatible operators. Ipamorelin engagement of GHS-R1a at compatible operators produces inositol trisphosphate and diacylglycerol as primary second messengers without significant activation of adrenocorticotropic hormone release pathways at compatible operators.
Comparison with GHRP-6 receptor activity
GHRP-6 binds to the ghrelin receptor with a lower selectivity than Ipamorelin, and in turn, the former is observed to cause measurable increases in cortisol levels alongside a rise in GH levels when administered to compatible operators. Co-secretion of cortisol from GHRP-6 at compatible operators is influenced by receptor binding at sites other than the pituitary, including hypothalamic neurons that influence the adrenocorticotropic axis at compatible operators.
GHRP-6 also produces appetite stimulation at compatible operators through ghrelin receptor engagement in hypothalamic feeding regulation circuits, which Ipamorelin’s more restricted receptor binding does not generate to an equivalent degree at compatible operators.
Comparison with GHRP-2 receptor activity
GHRP-2 at compatible operators binds the ghrelin receptor with higher potency than Ipamorelin, but also generates prolactin elevation that Ipamorelin’s selective binding does not produce at comparable receptor occupancy levels at compatible operators. GHRP-2’s prolactin co-secretion at compatible operators reflects receptor engagement at lactotroph cells or hypothalamic sites that Ipamorelin’s binding profile does not engage to an equivalent extent at compatible operators.
Receptor selectivity implications
IPAmorelin’s selective GHS-R1a binding at compatible operators limits the downstream effects of receptor-mediated co-secretion events to a narrower set of downstream effects than those produced at comparable doses at compatible operators by earlier growth hormone-releasing peptides. Ipamorelin is commonly used in conjunction with cortisol and prolactin co-secretion as a ghrelin receptor agonist of choice in research contexts that require separation of GH pathway from cortisol and prolactin co-secretion at compatible operators over less selective alternatives.
Ipamorelin’s GHS-R1a binding profile differs from GHRP-6 and GHRP-2 through higher receptor selectivity and a reduced co-secretion profile covering cortisol and prolactin. Research requiring GH pathway isolation from co-secretion variables applies Ipamorelin over less selective growth hormone-releasing peptide alternatives at compatible operators.
Comments