Distribution of orexin/hypocretin immunoreactivity in the brain of a male songbird, the house finch, Carpodacus mexicanus

Immunohistochemical localization of orexins (hypocretins) in the brain of reptiles and its relation to monoaminergic systems

“…This was also observed in amphibians (Galas et al, 2001;Singletary et al, 2005;Ló pez et al, 2009) and teleosts (Kaslin et al, 2004;Huesa et al, 2005;Amiya et al, 2007). In birds, the innervation of these mesencephalic regions is more conspicuous (Singletary et al, 2006), suggesting an important function for orexins in the auditory and visual system. Notably in mammals, the orexinergic innervation of midbrain structures is moderate to low (Nixon and Smale, 2007) but conspicuous innervation of the neurons of the mesencephalic trigeminal nucleus was seen in the rat (Stoyanova and Lazarov, 2005).…”

“…The dopaminergic cell groups of the substantia nigra/ventral tegmental area complex of reptiles are likely to be innervated by orexin-ir neurons, because abundant orexin-ir terminal structures were seen in their proximity, as in mammals and birds (Bubser et al, 2005;Singletary et al, 2006;Balcita-Pedicino and Sesack, 2007;present results). This situation is also shared by anamniotes, as demonstrated for several amphibians and teleosts (Kaslin et al, 2004;Ló pez et al, 2009).…”

“…The antisera anti-orexin-A and anti-orexin-B (both of Santa Cruz Biotechnology) used in this study, are raised against a peptide mapping at the C-terminus of orexin-A or orexin-B of human origin. This would explain why there were no differences in the pattern of staining that they yield (Singletary et al, 2005(Singletary et al, , 2006Ló pez et al, 2009), being impossible to discern between putative distinct distributions of different orexin peptides and only orexinimmunoreactivity, in general, could be investigated. In addition, the orexins do not have structural homology with other biologically active peptides (Shibahara et al, 1999).…”

“…Orexins in specific cells of the adenohypophysis have been reported in human (Blanco et al, 2003), orexin-A in two species of amphibian anurans (Yamamoto et al, 2004;Suzuki et al, 2007b) and orexin-A and orexin-B in the pituitary of two species of teleost fishes (Amiya et al, 2007;Suzuki et al, 2007aSuzuki et al, , 2009. However, none of the other studies in fishes, amphibians, birds or mammals detected orexin-ir cells in the hypophysis (Shibahara et al, 1999;Galas et al, 2001;Phillips-Singh et al, 2003;Kaslin et al, 2004;Huesa et al, 2005;Singletary et al, 2005Singletary et al, , 2006Nixon and Smale, 2007;Ló pez et al, 2009) and the hypophysis is devoid of orexin-ir cells in the two reptiles analyzed in the present study. This discrepancy may be an example of technical differences produced by the use of different antibodies.…”

“…However, due to the conserved molecular structure of orexins across vertebrates (Sakurai et al, 1998;Shibahara et al, 1999;Alvarez and Sutcliffe, 2002;Ohkubo et al, 2002), several studies have used antibodies against mammalian orexins to localize orexin-immunoreactive (orexin-ir) cell bodies and fibers in representatives of fish (Kaslin et al, 2004;Huesa et al, 2005;Amiya et al, 2007), amphibians (Shibahara et al, 1999;Galas et al, 2001;Singletary et al, 2005;Suzuki et al, 2008;Ló pez et al, 2009) and birds (Ohkubo et al, 2002;Phillips-Singh et al, 2003;Singletary et al, 2006). The results of these studies suggested a highly conserved organization of orexinergic systems in the brain of vertebrates.…”