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Hypothalamic and zona incerta neurons expressing hypocretin, but not melanin concentrating hormone, project to the hamster intergeniculate leaflet
- Source :
-
Neuroscience . Nov2005, Vol. 134 Issue 3, p1081-1090. 10p. - Publication Year :
- 2005
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Abstract
- Abstract: The hypocretins (Hcrt; also known as orexins) and melanin-concentrating hormone comprise distinct families of neuropeptides synthesized in cells located in the lateral hypothalamus and adjacent areas. The Hcrts are thought to modulate food intake and sleep/wake patterns in mammals. Melanin-concentrating hormone has a well-documented role in energy metabolism. A moderate plexus of Hcrt immunoreactive terminals has been described in the hamster intergeniculate leaflet, part of the circadian rhythm system. This study investigated the origin of Hcrt-immunoreactive terminals in the intergeniculate leaflet and determined whether melanin-concentrating hormone neurons also project to the intergeniculate leaflet. The tracer, cholera toxin β-subunit, was injected into the intergeniculate leaflet of the golden hamster. Double-label fluorescent immunohistochemistry for cholera toxin β-subunit and Hcrt or melanin-concentrating hormone was then performed to identify retrogradely labeled cells also containing immunoreactive peptide. Most cholera toxin β-subunit-labeled cells were detected in the medial zona incerta and sub-incertal zone, with few observed in the lateral hypothalamus. Hcrt-immunoreactive cells were abundant and found largely in the lateral hypothalamus and adjacent nuclei. Melanin-concentrating hormone cells were also abundant in the medial zona incerta, in close proximity to cholera toxin β-subunit-labeled cells, but ventral to them. Cells containing both cholera toxin β-subunit and Hcrt-immunoreactive, were present in the dorsal aspect of the lateral hypothalamus. The number observed was small, ≤1% of the total number of Hcrt cells counted in the hamster. No cholera toxin β-subunit-immunoreactive cells also contained melanin-concentrating hormone and no melanin-concentrating hormone-immunoreactive processes were evident in the intergeniculate leaflet. The results show that a small number of lateral hypothalamus cells containing Hcrt-immunoreactivity project to the intergeniculate leaflet, but they are scattered rather than collected into a discrete group. At the present time there is no information regarding the function of these cells, although they may contribute to the regulation of sleep/arousal, circadian rhythmicity, or vestibulo-oculomotor function. [Copyright &y& Elsevier]
- Subjects :
- *HYPOTHALAMIC hormones
*NEURONS
*NERVOUS system
*OREXINS
Subjects
Details
- Language :
- English
- ISSN :
- 03064522
- Volume :
- 134
- Issue :
- 3
- Database :
- Academic Search Index
- Journal :
- Neuroscience
- Publication Type :
- Academic Journal
- Accession number :
- 18240446
- Full Text :
- https://doi.org/10.1016/j.neuroscience.2005.03.062