PT-141 is a synthetic cyclic heptapeptide that acts as an agonist at melanocortin receptors, particularly the MC3R and MC4R subtypes. Structurally it is a cyclic lactam peptide related to the melanocortin analog MT-2, from which it differs by the absence of the linear C-terminal tail. It is studied in preclinical, in-vitro models for its binding to the melanocortin receptor family and the downstream signaling those receptors drive.
The Melanocortin System
The melanocortin system is a neuroendocrine signaling network consisting of five G protein-coupled receptor subtypes (MC1R through MC5R) and their endogenous peptide ligands, which are derived from the precursor protein proopiomelanocortin (POMC). The melanocortin receptors are distributed across diverse tissues and mediate a wide range of physiological functions. MC1R is primarily expressed in melanocytes and is involved in pigmentation. MC2R is the ACTH receptor in adrenal cortex. MC3R and MC4R are expressed in the central nervous system and are studied for their roles in neuroendocrine signaling. MC5R is found in exocrine glands.
PT-141 is of particular research interest because of its activity at MC3R and MC4R, both of which are expressed in central nervous system regions including the hypothalamus, limbic system, and brainstem. In cell and animal models these receptors are used to study melanocortin signal transduction and the integration of neural inputs at the receptor level.
Receptor Binding Profile
In-vitro receptor binding studies have characterized PT-141 as a non-selective agonist with activity at multiple melanocortin receptor subtypes, with particular potency at MC3R and MC4R. Competitive binding assays using radiolabeled NDP-MSH (a reference melanocortin agonist) have demonstrated that PT-141 displaces the radioligand from MC4R with nanomolar affinity. Functional assays measuring cyclic AMP accumulation in cells expressing individual melanocortin receptor subtypes have confirmed agonist activity at MC1R, MC3R, MC4R, and MC5R, with minimal activity at MC2R.
This receptor binding profile distinguishes PT-141 from alpha-MSH and other endogenous melanocortin peptides. Researchers studying melanocortin receptor pharmacology have used PT-141 alongside selective agonists and antagonists to map the functional contributions of individual receptor subtypes to the signaling responses measured in cell and animal models.
CNS Signaling Research
The central signaling of PT-141 has been a focus of preclinical investigation. Research using c-Fos immunohistochemistry, a marker of neuronal activation, has shown that exposure to PT-141 in rodent models activates neurons in the paraventricular nucleus of the hypothalamus and other brain regions expressing melanocortin receptors.
Electrophysiological studies in brain slice preparations have demonstrated that melanocortin receptor activation modulates excitatory and inhibitory synaptic transmission in hypothalamic circuits. These studies have contributed to the understanding of how the melanocortin system integrates diverse neural inputs at the receptor level, a fundamental question in neuroendocrinology research.
Preclinical Study Design Considerations
Researchers working with PT-141 in preclinical models should be aware of several considerations. Concentration-response relationships have been characterized across species, with effective concentrations varying considerably between rodent and primate model systems. As with all melanocortin agonists, assay design should account for the non-selective activity of the compound across multiple receptor subtypes when attributing a measured signal to a specific receptor.
PT-141 is supplied as a lyophilized powder and should be stored at negative twenty degrees Celsius. Reconstitution with bacteriostatic water produces a clear solution that should be refrigerated at two to eight degrees Celsius and used within three weeks. Purity and identity should be confirmed via HPLC and mass spectrometry with each lot.
Research Use Disclaimer
PT-141 is provided exclusively for in-vitro and preclinical research use. It is not sold for human consumption or therapeutic application. All pharmacological data presented in this article is derived from preclinical studies in cell culture systems and animal models. Researchers must ensure compliance with all applicable regulatory requirements and institutional oversight when incorporating PT-141 into experimental protocols.