Expression of the melanin-concentrating hormone (MCH) receptor mRNA in therat brain

The melanin-concentrating hormone (MCH) system is thought to be an importan t regulator of food intake. Recently the orphan G protein-coupled receptor SLC-1 was identified as the MCH receptor (MCHR). Preliminary analyses of MC HR mRNA distribution have supported a role for the MCH system in nutritiona l homeostasis. We report here a complete anatomical distribution of the MCH R mRNA. We have found high levels of expression of MCHR mRNA in most anatom ical areas implicated in control of olfaction, with the exception of the ma in olfactory bulb. Dense labeling was also detected in the hippocampal form ation, subiculum, and basolateral amygdala, all of which are important in l earning and memory, and in the shell of the nucleus accumbens, a substrate for motivated behavior and feeding. Within the hypothalamus, MCHR mRNA was moderately expressed in the ventromedial nucleus, arcuate nucleus, and zona incerta, all of which serve key roles in the neuronal circuitry of feeding . In the brainstem, strong expression was observed in the locus coeruleus, which is implicated in arousal, as well as in nuclei that contribute to oro facial function and mastication, including the facial, hypoglossal, motor t rigeminal, and dorsal motor vagus nuclei. In most regions there was a good correspondence between MCHR mRNA distribution and that of MCH-immunoreactiv e fibers. Taken together, these data suggest that MCH may act at various le vels of the brain to integrate various aspects of feeding behavior. However , the extensive MCHR distribution throughout the brain suggests that this r eceptor may play a role in other functions, most notably reinforcement, aro usal, sensorimotor integration, and autonomic control. a zool Wiley-Liss, I nc.