Rat Prolactin Receptor (PRLR) is a transmembrane receptor belonging to the class I cytokine receptor family, which also includes receptors for growth hormone (GHR), erythropoietin (EPOR), and several interleukins that signal through related intracellular pathways. In rats (Rattus norvegicus), PRLR binds the hormone prolactin (PRL) and activates intracellular signaling cascades primarily through the JAK2/STAT5 pathway, as well as MAPK and PI3K/AKT pathways, leading to regulation of genes involved in cell proliferation, differentiation, and metabolic function. Rat PRLR is expressed in multiple tissues including the mammary gland, ovary, uterus, liver, brain, adipose tissue, and immune cells, where it mediates the diverse physiological actions of prolactin. PRLR signaling plays essential roles in mammary gland development, lactation, reproductive function, and maternal behavior, and also contributes to metabolic regulation and immune modulation. In addition to the membrane-bound receptor, soluble forms of rat PRLR (sPRLR) can arise through alternative splicing or proteolytic cleavage, generating extracellular receptor fragments that can bind circulating prolactin and potentially regulate hormone availability and signaling activity. Because rats are widely used in endocrinology, reproductive biology, and neuroendocrine research, characterization of rat PRLR has contributed significantly to understanding prolactin signaling, hormonal control of reproduction and lactation, and interactions between endocrine and immune systems relevant to mammalian physiology.