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A comparative analysis shows morphofunctional differences between the rat and mouse melanin-concentrating hormone systems.

Croizier S, Franchi-Bernard G, Colard C, Poncet F, La Roche A, Risold PY - PLoS ONE (2010)

Bottom Line: Sub-populations of neurons producing melanin-concentrating hormone (MCH) are characterized by distinct projection patterns, birthdates and CART/NK3 expression in rat.Evidence for such sub-populations has not been reported in other species.Furthermore, divergences in the distribution of MCH axons were observed, in particular in the ventromedial hypothalamus.

View Article: PubMed Central - PubMed

Affiliation: Faculté de Médecine et de Pharmacie, Université de Franche-Comté, Besançon, France.

ABSTRACT
Sub-populations of neurons producing melanin-concentrating hormone (MCH) are characterized by distinct projection patterns, birthdates and CART/NK3 expression in rat. Evidence for such sub-populations has not been reported in other species. However, given that genetically engineered mouse lines are now commonly used as experimental models, a better characterization of the anatomy and morphofunctionnal organization of MCH system in this species is then necessary. Combining multiple immunohistochemistry experiments with in situ hybridization, tract tracing or BrdU injections, evidence supporting the hypothesis that rat and mouse MCH systems are not identical was obtained: sub-populations of MCH neurons also exist in mouse, but their relative abundance is different. Furthermore, divergences in the distribution of MCH axons were observed, in particular in the ventromedial hypothalamus. These differences suggest that rat and mouse MCH neurons are differentially involved in anatomical networks that control feeding and the sleep/wake cycle.

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Diagrams summarizing differences between rat and mouse MCH systems.Summary diagrams to compare the genesis of MCH, Hcrt neuron populations and MCH/CART/NK3 sub-population. In mouse (A), both peaks of MCH and Hcrt production are at E10. MCH/CART/NK3 neurons are generated after E10 and constitute less than half of the whole MCH population. In rat (B), the peak of MCH production is late compared to the peak of Hcrt genesis, and in this species MCH/CART/NK3 neurons form 2/3 of the whole MCH population. It can be hypothesize that these different patterns of genesis have an impact on the organization of the MCH neuron system in the two species: in mouse (C), MCH type A neurons is preeminent compared to MCH type B neurons. On the contrary, MCH type B neurons is better represented in rat (D), and a group of lastly generated cells with a periventricular distribution and projections in the arcuate nucleus (MCH type C neurons) can be observed. This last group is lacking in mouse.
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pone-0015471-g009: Diagrams summarizing differences between rat and mouse MCH systems.Summary diagrams to compare the genesis of MCH, Hcrt neuron populations and MCH/CART/NK3 sub-population. In mouse (A), both peaks of MCH and Hcrt production are at E10. MCH/CART/NK3 neurons are generated after E10 and constitute less than half of the whole MCH population. In rat (B), the peak of MCH production is late compared to the peak of Hcrt genesis, and in this species MCH/CART/NK3 neurons form 2/3 of the whole MCH population. It can be hypothesize that these different patterns of genesis have an impact on the organization of the MCH neuron system in the two species: in mouse (C), MCH type A neurons is preeminent compared to MCH type B neurons. On the contrary, MCH type B neurons is better represented in rat (D), and a group of lastly generated cells with a periventricular distribution and projections in the arcuate nucleus (MCH type C neurons) can be observed. This last group is lacking in mouse.

Mentions: Without any doubt, dissimilarities between rat and mouse MCH systems are related to divergences in their developmental differentiation (Figure 9). In agreement with classical birthdating studies, we observed that neurons settle in the hypothalamus following a lateral to medial gradient in mouse as in rat; first-wave generated neurons lay close to the cerebral peduncle, and lastly produced cells are periventricular [19]–[21]. In rat, the peak of MCH genesis correlates with the production of MCH/CART/NK3 cell bodies, and is slightly late compared to the peak of Hcrt neuron genesis. In mice we observed that both MCH and Hcrt peaks coincided, but that MCH/CART/NK3 neuron production is still later than Hcrt genesis. We can conclude that compared to Hcrt genesis, the peak of MCH production is a little more precocious in mouse than in rat and MCH/CART neurons are less abundant. A slightly more precocious MCH production could also explain the absence of MCH neurons in the PVp. We know that these neurons are produced last in the rat [12]; maybe MCH neuron production in mice ends before the differentiation of a MCH cell group in this periventricular nucleus. In the past, we used a specific nomenclature in the rat to identify MCH neuron sub-populations [23]: MCH type A neurons for spinally MCH projecting cells, and MCH type B neurons for MCH/CART cortically projecting cells [13],[14],[23]. We also suspected that, in the rat, the latest produced cells (including those in the PVp), which are never labeled after retrograde injections in the cerebral cortex nor the spinal cord, could be grouped into a MCH type C sub-population [14]. In rat, MCH type B neurons are prominent. In mouse, MCH type A neurons are more abundant, and as their production peak is coincident with the Hcrt peak, they may also project with these neurons in the cerebral cortex. With an early peak of MCH genesis, fewer cells are observed medial to the fornix and MCH type C neurons are rare in this species, with very few MCH projections in the arcuate nucleus.


A comparative analysis shows morphofunctional differences between the rat and mouse melanin-concentrating hormone systems.

Croizier S, Franchi-Bernard G, Colard C, Poncet F, La Roche A, Risold PY - PLoS ONE (2010)

Diagrams summarizing differences between rat and mouse MCH systems.Summary diagrams to compare the genesis of MCH, Hcrt neuron populations and MCH/CART/NK3 sub-population. In mouse (A), both peaks of MCH and Hcrt production are at E10. MCH/CART/NK3 neurons are generated after E10 and constitute less than half of the whole MCH population. In rat (B), the peak of MCH production is late compared to the peak of Hcrt genesis, and in this species MCH/CART/NK3 neurons form 2/3 of the whole MCH population. It can be hypothesize that these different patterns of genesis have an impact on the organization of the MCH neuron system in the two species: in mouse (C), MCH type A neurons is preeminent compared to MCH type B neurons. On the contrary, MCH type B neurons is better represented in rat (D), and a group of lastly generated cells with a periventricular distribution and projections in the arcuate nucleus (MCH type C neurons) can be observed. This last group is lacking in mouse.
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Related In: Results  -  Collection

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pone-0015471-g009: Diagrams summarizing differences between rat and mouse MCH systems.Summary diagrams to compare the genesis of MCH, Hcrt neuron populations and MCH/CART/NK3 sub-population. In mouse (A), both peaks of MCH and Hcrt production are at E10. MCH/CART/NK3 neurons are generated after E10 and constitute less than half of the whole MCH population. In rat (B), the peak of MCH production is late compared to the peak of Hcrt genesis, and in this species MCH/CART/NK3 neurons form 2/3 of the whole MCH population. It can be hypothesize that these different patterns of genesis have an impact on the organization of the MCH neuron system in the two species: in mouse (C), MCH type A neurons is preeminent compared to MCH type B neurons. On the contrary, MCH type B neurons is better represented in rat (D), and a group of lastly generated cells with a periventricular distribution and projections in the arcuate nucleus (MCH type C neurons) can be observed. This last group is lacking in mouse.
Mentions: Without any doubt, dissimilarities between rat and mouse MCH systems are related to divergences in their developmental differentiation (Figure 9). In agreement with classical birthdating studies, we observed that neurons settle in the hypothalamus following a lateral to medial gradient in mouse as in rat; first-wave generated neurons lay close to the cerebral peduncle, and lastly produced cells are periventricular [19]–[21]. In rat, the peak of MCH genesis correlates with the production of MCH/CART/NK3 cell bodies, and is slightly late compared to the peak of Hcrt neuron genesis. In mice we observed that both MCH and Hcrt peaks coincided, but that MCH/CART/NK3 neuron production is still later than Hcrt genesis. We can conclude that compared to Hcrt genesis, the peak of MCH production is a little more precocious in mouse than in rat and MCH/CART neurons are less abundant. A slightly more precocious MCH production could also explain the absence of MCH neurons in the PVp. We know that these neurons are produced last in the rat [12]; maybe MCH neuron production in mice ends before the differentiation of a MCH cell group in this periventricular nucleus. In the past, we used a specific nomenclature in the rat to identify MCH neuron sub-populations [23]: MCH type A neurons for spinally MCH projecting cells, and MCH type B neurons for MCH/CART cortically projecting cells [13],[14],[23]. We also suspected that, in the rat, the latest produced cells (including those in the PVp), which are never labeled after retrograde injections in the cerebral cortex nor the spinal cord, could be grouped into a MCH type C sub-population [14]. In rat, MCH type B neurons are prominent. In mouse, MCH type A neurons are more abundant, and as their production peak is coincident with the Hcrt peak, they may also project with these neurons in the cerebral cortex. With an early peak of MCH genesis, fewer cells are observed medial to the fornix and MCH type C neurons are rare in this species, with very few MCH projections in the arcuate nucleus.

Bottom Line: Sub-populations of neurons producing melanin-concentrating hormone (MCH) are characterized by distinct projection patterns, birthdates and CART/NK3 expression in rat.Evidence for such sub-populations has not been reported in other species.Furthermore, divergences in the distribution of MCH axons were observed, in particular in the ventromedial hypothalamus.

View Article: PubMed Central - PubMed

Affiliation: Faculté de Médecine et de Pharmacie, Université de Franche-Comté, Besançon, France.

ABSTRACT
Sub-populations of neurons producing melanin-concentrating hormone (MCH) are characterized by distinct projection patterns, birthdates and CART/NK3 expression in rat. Evidence for such sub-populations has not been reported in other species. However, given that genetically engineered mouse lines are now commonly used as experimental models, a better characterization of the anatomy and morphofunctionnal organization of MCH system in this species is then necessary. Combining multiple immunohistochemistry experiments with in situ hybridization, tract tracing or BrdU injections, evidence supporting the hypothesis that rat and mouse MCH systems are not identical was obtained: sub-populations of MCH neurons also exist in mouse, but their relative abundance is different. Furthermore, divergences in the distribution of MCH axons were observed, in particular in the ventromedial hypothalamus. These differences suggest that rat and mouse MCH neurons are differentially involved in anatomical networks that control feeding and the sleep/wake cycle.

Show MeSH