Orexinergic innervation of POMC-containing neurons in the rat arcuate nucleus

Abstract

A pre-embedding double immunostaining technique was used to study the synaptic relationships between orexin-like immunoreactive axon terminals and preopiomelanocortin (POMC)-like immunoreactive neurons in the rat arcuate nucleus. Most of the synapses were axo-dendritic, while some axo-somatic synapses were also found. Both the axo-somatic and axodendritic synapses were symmetrical. In some cases the presynaptic orexin-like immunoreactive axon terminals contained a few large dense-cored vesicles. The results suggest that the orexinergic axon terminals in the arcuate nucleus may play an important role in the regulation of food intake via synapses through POMC neurons.

Reciprocal synaptic relationships between orexin- and melanin-concentrating hormone-containing neurons in the rat lateral hypothalamus: a novel circuit implicated in feeding regulation

“…Our finding is in accordance with other reports. 15,18,23 However, although the ORX-LI axon terminals have been reported as exclusively making asymmetrical synapses, 21,22 we did find a low frequency of symmetrical synapses.…”

“…Although the ultrastructure of ORX-LI axon terminals has been studied several times in the rat arcuate nucleus 18,21 and locus coeruleus 22 where the axon terminals have been demonstrated to synapse on neuropeptide Y, 21 POMC 18 and noradrenaline 220 producing neurons, no work has dealt directly with ORX-LI neurons in the rat LH. For this reason, we examined the ORX-LI neuron in the LH at the electron microscopic level.…”

Electrical Inhibition of Identified Anorexigenic POMC Neurons by Orexin/Hypocretin

“…Orexin-containing terminals are found on and around ARC POMC neurons Guan et al, 2001;Muroya et al, 2004), and the release of orexin is highest during active, awake periods (Kiyashchenko et al, 2002). Considering the appetite-suppressing influence of POMC neurons, their electrical inhibition by orexin, described here, may help to ensure that food seeking coincides with periods when the animal is most alert and active.…”

“…ARC POMC cells are surrounded by orexin-containing nerve terminals (Guan et al, 2001;Muroya et al, 2004), and there is strong orexin receptor-1 immunoreactivity in and around ARC POMC cells (Backberg et al, 2002;Suzuki et al, 2002). Microinjection of orexin into the ARC stimulates feeding (Muroya et al, 2004), and orexin reduces intracellular Ca 2ϩ levels in isolated POMC neurons (Muroya et al, 2004), suggesting that orexin may suppress the electrical activity of the anorexigenic POMC cells.…”

Contrôle de la glycémie par l’axe nerveux intestin-cerveau

“…De nombreuses études, depuis une vingtaine d'années, ont cherché à identifier les populations neuronales hypothalamiques qui contiennent des neurotransmetteurs et des récepteurs spécifiques d'importance cruciale dans le comportement alimentaire et la régulation de la glycémie. Parmi les noyaux hypothalamiques, le noyau arqué (ARC) occupe un rôle intégrateur majeur, avec des connexions à la zone laté-rale, au tronc cérébral et au système cortico-limbique, entre autres [7] (Figure 1). Plusieurs populations neuronales ont été identifiées dans l'hypothalamus, sur la base de leur contenu en neurotransmetteurs.…”