The prairie vole vomeronasal organ is a target for gonadotropin-releasing hormone

Gonadotropin-releasing hormone (GnRH) is present in nervus terminalis neurons in chemosensory nerve fascicles in vertebrates. In rodents, the majority of GnRH fibers are located within vomeronasal nerves. We have shown that GnRH can alter vomeronasal receptor neuron responses to odors. In this study, using prairie voles, we tested the hypotheses that (i) GnRH-immunoreactive (-ir) neurons project to the vomeronasal organ and accessory olfactory bulb; (ii) a radioactive-labeled GnRH agonist, buserelin, binds to vomeronasal sensory neurons; and (iii) vomeronasal receptor cells express GnRH receptor mRNA as evidenced by reverse transcription-polymerase chain reaction (RT-PCR) combined with Southern blotting. In neonatal voles, GnRH-ir cell bodies and fibers were observed within the vomeronasal epithelium, vomeronasal nerves and accessory olfactory bulbs. In adult voles, GnRH-ir fibers were observed not only in the lamina propria of the vomeronasal mucosa, but also along vomeronasal nerves and in the accessory olfactory bulb. Binding of [(125)I]buserelin was observed specifically over the vomeronasal sensory epithelium, and RT-PCR/Southern blotting demonstrated GnRH receptor expression in the vomeronasal mucosa, as well as in olfactory epithelium and pterygopalatine ganglion, two additional structures containing GnRH-ir neurons of the nervus terminalis. This study supports the hypothesis that GnRH is released from nervus terminalis fibers to modulate chemosensory processes, especially those involving chemoreception in the vomeronasal organ.