Anatomical organization of MCH connections with the pallidum and dorsal striatum in the rat.

Sandrine Chometton,Amandine Mariot,Gabrielle Franchi,Vesna Cvetkovic-Lopes,Christophe Houdayer,Fabrice Poncet,Pierre-Yves Risold,Dominique Fellmann

doi:10.3389/fnsys.2014.00185

Sandrine Chometton, Amandine Mariot + Show 6 more

Open Access

https://doi.org/10.3389/fnsys.2014.00185

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Abstract

Neurons producing the melanin-concentrating hormone (MCH) are distributed in the posterior hypothalamus, but project massively throughout the forebrain. Many aspects regarding the anatomical organization of these projections are still obscure. The present study has two goals: first to characterize the topographical organization of neurons projecting into the cholinergic basal forebrain (globus pallidus, medial septal complex), and second to verify if MCH neurons may indirectly influence the dorsal striatum (caudoputamen) by innervating afferent sources to this structure. In the first series of experiments, the retrograde tracer fluorogold was injected into multiple sites in the pallidal and medial septal regions and the distribution of retrogradely labeled neurons were analyzed in the posterior lateral hypothalamus. In the second series of experiments, fluorogold was injected into the caudoputamen, and the innervation by MCH axons of retrogradely labeled cells was analyzed. Our results revealed that the MCH system is able to interact with the basal nuclei in several different ways. First, MCH neurons provide topographic inputs to the globus pallidus, medial septal complex, and substantia innominata. Second, striatal projecting neurons in the cortex, thalamus, and substantia nigra presumably receive only sparse inputs from MCH neurons. Third, the subthalamic nucleus is heavily innervated by MCH projections, thus, presumably serves as one important intermediate station to mediate MCH influence on other parts of the basal nuclei.

Highlights

Melanin-concentrating hormone (MCH)-containing neurons in the hypothalamus send extensive projections throughout the cerebral cortex (Bittencourt et al, 1992; Risold et al, 1997)
The magnocellular cholinergic neurons in the basal forebrain are abundant across the borders of the medial septal complex, the magnocellular preoptic nucleus, the substantia innominata www.frontiersin.org and most the internal segment of the globus pallidus
MCH projections arising from the medial forebrain bundle are abundant in the cholinergic rich regions of both the medial septal complex and the globus pallidus, while the parvalbumin-rich part of the septum received “en passant” inputs as already reported elsewhere (Croizier et al, 2010) (Figure 1)

Summary

Introduction

Melanin-concentrating hormone (MCH)-containing neurons in the hypothalamus send extensive projections throughout the cerebral cortex (Bittencourt et al, 1992; Risold et al, 1997). In The overall organization of an anatomical circuitry linking the MCH system to the striato-pallido-nigral pathway is unknown at this point

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