Localization of LGR7 (relaxin receptor) mRNA and protein in rat forebrain: correlation with relaxin binding site...

Discrete neuronal populations in brain express relaxin and relaxin-3, and molecular studies have identified former-orphan, G-protein-coupled receptors LGR7 and GPCR135 as their native receptors. To better understand the role of central relaxin systems, we began to assess the anatomic distribution of these receptors and ligands in brain. This study documents the widespread distribution of LGR7 mRNA and LGR7-like immunoreactivity (LI) throughout adult rat forebrain areas shown to contain specific [33P]-relaxin binding sites. High densities of LGR7 mRNA hybridization were detected in deep layers of neocortex, hypothalamic paraventricular and supraoptic nuclei and within hippocampal subiculum and CA3, the basolateral amygdala and subfornical organ. Low to moderate hybridization was detected in septum, midline thalamic nuclei, arcuate and supramammillary nuclei, and regions of the midbrain pons. Complementary expression of LGR7-LI was observed in cortical pyramidal neurons, hypothalamic magnocellular neurons, and hippocampal pyramidal and interneurons. These findings provide further evidence for actions of relaxin as a modulator in somatosensory, autonomic, and neuroendocrine pathways.