β-Endorphin, equine (TFA) is an endogenous opioid peptide, which binds at high affinity to both μ/δ opioid receptors[1][2]. Analgesic properties[2].
[1]. Yahav Dikshtein, et al. β-Endorphin via the Delta Opioid Receptor is a Major Factor in the Incubation of Cocaine Craving. Neuropsychopharmacology. 2013 Nov; 38(12): 2508-2514. [2]. NiinistÖ KE, et al. Plasma levels of heat shock protein 72 (HSP72) and beta-endorphin as indicators of stress, pain and prognosis in horses with colic. Vet J. 2010 Apr;184(1):100-4.