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Nuclear organization of orexinergic neurons in the hypothalamus of a lar gibbon and a chimpanzee |
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| Authors: | Victoria M Williams Adhil Bhagwandin Jordan Swiegers Mads F Bertelsen Therese Hård Thomas C Thannickal Jerome M Siegel Chet C Sherwood Paul R Manger |
| Institution: | 1. School of Anatomical Sciences, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, Republic of South Africa
Contribution: Conceptualization (equal), Data curation (equal), Formal analysis (equal), Investigation (equal), Methodology (equal), Writing - original draft (equal);2. School of Anatomical Sciences, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, Republic of South Africa Division of Clinical Anatomy and Biological Anthropology, Department of Human Biology, University of Cape Town, Cape Town, South Africa Contribution: Data curation (equal), Formal analysis (equal), Investigation (equal), Methodology (equal), Writing - review & editing (equal);3. School of Anatomical Sciences, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, Republic of South Africa Contribution: Formal analysis (equal), Investigation (equal), Methodology (equal), Writing - review & editing (equal);4. Centre for Zoo and Wild Animal Health, Copenhagen Zoo, Frederiksberg, Denmark Contribution: Investigation (equal), Methodology (equal), Writing - review & editing (equal);5. Borås Zoo, Borås, Sweden Contribution: Investigation (equal), Methodology (equal), Writing - review & editing (equal);6. Department of Psychiatry, School of Medicine, and Brain Research Institute, University of California, Los Angeles, Los Angeles, California, USA Brain Research Institute, Neurobiology Research, Sepulveda VA Medical Center, Los Angeles, California, USA Contribution: Formal analysis (equal), Investigation (equal), Methodology (equal), Writing - review & editing (equal);7. Department of Anthropology and Center for the Advanced Study of Human Paleobiology, The George Washington University, Washington, District of Columbia, USA Contribution: Conceptualization (equal), Formal analysis (equal), Funding acquisition (equal), Investigation (equal), Methodology (equal), Supervision (equal), Writing - review & editing (equal);8. School of Anatomical Sciences, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, Republic of South Africa |
| Abstract: | Employing orexin-A immunohistochemical staining we describe the nuclear parcellation of orexinergic neurons in the hypothalami of a lar gibbon and a chimpanzee. The clustering of orexinergic neurons within the hypothalamus and the terminal networks follow the patterns generally observed in other mammals, including laboratory rodents, strepsirrhine primates and humans. The orexinergic neurons were found within three distinct clusters in the ape hypothalamus, which include the main cluster, zona incerta cluster and optic tract cluster. In addition, the orexinergic neurons of the optic tract cluster appear to extend to a more rostral and medial location than observed in other species, being observed in the tuberal region in the anterior ventromedial aspect of the hypothalamus. While orexinergic terminal networks were observed throughout the brain, high density terminal networks were observed within the hypothalamus, medial and intralaminar nuclei of the dorsal thalamus, and within the serotonergic and noradrenergic regions of the midbrain and pons, which is typical for mammals. The expanded distribution of orexinergic neurons into the tuberal region of the ape hypothalamus, is a feature that needs to be investigated in other primate species, but appears to correlate with orexin gene expression in the same region of the human hypothalamus, but these neurons are not revealed with immunohistochemical staining in humans. Thus, it appears that apes have a broader distribution of orexinergic neurons compared to other primate species, but that the neurons within this extension of the optic tract cluster in humans, while expressing the orexin gene, do not produce the neuropeptide. |
| Keywords: | ape brain evolution hypocretin immunohistochemistry orexin primates |