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Marcelino Aviles-Trigueros, Francisca Matínez-Garrido, Francisco Nadal-Nicolás, Marta Agudo-Barriuso, Inmaculada Selles-Navarro, Manuel Vidal-Sanz; Melanopsin-like Photopigment Expression In Adult Mammal Brain. Invest. Ophthalmol. Vis. Sci. 2012;53(14):4336.
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Melanopsin is a novel non-canonical photopigment present in a subset of retinal ganglion cells in the mammal’s eye which is responsible for several light mediated physiological functions (including circadian entrainment) that are not related to image forming vision. In non-mammalian vertebrates, melanopsin is expressed in both ocular and non-ocular photoreceptors; however, mammalian melanopsin is restricted to the cell bodies, dendrites and proximal axons of melanopsin containing retinal cells. The aim of this research is to investigate melanopsin expression in the adult mammalian brain.
To investigate the presence of melanopsin expressing cell bodies and projections, serial coronal sections from the brain of adult female Sprague-Dawley rats were obtained in the cryostat and processed for immunohistochemistry with commercial polyclonal antibodies against the melanopsin C- or N-terminal sequences. Western blots of protein extracts from retina, cortex, brainstem, or cerebellum homogenates were probed with the same antisera to detect melanopsin expression.
Immunohistochemistry shows a strong and specific expression of melanopsin in the brain, with high expression in selected areas of the hypothalamus such as the ventrolateral preoptic nucleus, the supraoptic nucleus, the paraventricular nucleus, the median eminence, and the infundibular stem, all of which form part of the hypothalamo-hypophyseal axis. Some of these areas receive direct innervation from melanopsin retinal ganglion cells, including the suprachiasmatic nucleus (Hattar et al, J Comp Neurol 2006, 497:326). In addition, western blotting detected melanopsin expression in other regions of the brain such as the cortex, brainstem, and cerebellum.
This is the first time that melanopsin expression is identified in the mammalian brain where it may play a role in nonimage forming visual functions.
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