Melanin-concentrating hormone projections to the dorsal raphe nucleus: An immunofluorescence and in vivo microdialysis study

Publication date: March 2016 Source:Journal of Chemical Neuroanatomy, Volume 72 Author(s): Jessika Urbanavicius, Patricia Lagos, Pablo Torterolo, Juan A. Abin-Carriquiry, Cecilia Scorza Melanin-concentrating hormone (MCH)-containing neurons are localized in the lateral hypothalamus and incerto-hypothalamic areas, and project to several brain regions including the dorsal raphe nucleus (DRN). The MCHergic system has been involved in the regulation of emotional states and we have demonstrated that MCH microinjections into the rat DRN promote a depressive-like state. To understand the MCHergic transmission into the DRN, in the present study we characterized the distribution and density of the MCHergic fibers along the rostro-caudal axis of the rat DRN and their anatomical relationship with the 5-HT- and GABA-containing neurons. Additionally, a functional in vivo microdialysis study was carried out in order to evaluate the MCH effects on the 5-HT extracellular levels. Immunolabeling studies showed that MCHergic fibers were widely distributed throughout the rostro-caudal DRN extent and a reduced density at the most caudal level was observed. Interestingly, MCHergic fibers appeared in close apposition to 5-HT and GABA-containing neurons. Microdialysis studies evidenced an opposite effect of two concentrations of MCH on 5-HT levels: the lower concentration (30μM) produced a significant and long-lasting (up to 120min) decrease while the higher (100μM) induced a slight ...
Source: Journal of Chemical Neuroanatomy - Category: Neuroscience Source Type: research