title: Cellular location and major terminal networks of the orexinergic system in the brain of two megachiropterans.
abstract: The present study describes the distribution of orexin-A immunoreactive neurons and their terminal networks in the brains of two species of megachiropterans. In general the organization of the orexinergic system in the mammalian brain is conserved across species, but as one of two groups of mammals that fly and have a high metabolic rate, it was of interest to determine whether there were any specific differences in the organization of this system in the megachiropterans. Orexinergic neurons were limited in distribution to the hypothalamus, and formed three distinct clusters, or nuclei, a main cluster with a perifornical location, a zona incerta cluster in the dorsolateral hypothalamus and an optic tract cluster in the ventrolateral hypothalamus. The nuclear parcellation of the orexinergic system in the megachiropterans is similar to that seen in many mammals, but differs from the microchiropterans where the optic tract cluster is absent. The terminal networks of the orexinergic neurons in the megachiropterans was similar to that seen in a range of mammalian species, with significant terminal networks being found in the hypothalamus, cholinergic pedunculopontine and laterodorsal tegemental nuclei, the noradrenergic locus coeruleus complex, all serotonergic nuclei, the paraventricular nuclei of the epithalamus and adjacent to the habenular nuclei. While the megachiropteran orexinergic system is typically mammalian in form, it does differ from that reported for microchiropterans, and thus provides an additional neural character arguing for independent evolution of these two chiropteran suborders.
authors.affiliation: School of Anatomical Sciences, Faculty of Health Sciences, University of the Witwatersrand, 7 York Road, Parktown 2193, Johannesburg, South Africa.
authors.forename: Leigh-Anne
authors.initials: LA
authors.lastname: Dell
authors.forename: Jean-Leigh
authors.initials: JL
authors.lastname: Kruger
authors.forename: John D
authors.initials: JD
authors.lastname: Pettigrew
authors.forename: Paul R
authors.initials: PR
authors.lastname: Manger
mesh_terms: D000818:Animals; D001921:Brain / Q000166:cytology* / Q000378:metabolism*; D002685:Chiroptera / Q000033:anatomy & histology / Q000378:metabolism; D007150:Immunohistochemistry; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism*; D009474:Neurons / Q000166:cytology* / Q000378:metabolism*; D009479:Neuropeptides / Q000378:metabolism*; D000068797:Orexins
chemical_list: D047908:Intracellular Signaling Peptides and Proteins; D009479:Neuropeptides; D000068797:Orexins
keywords: 3V; 4V; A15d; A15v; A6c; A6d; A7d; Amyg; C; CLi; Chiroptera; DRd; DRif; DRl; DRp; DRv; DT; Evolution; GP; Hbm; Hip; Hyp; Hypocretin; Mammalia; Mc; Megabat; Neuromodulatory systems; OT; Orexin; Otc; PV; R; RMg; RVL; Zic; amygdala; anterior hypothalamic group, dorsal division; anterior hypothalamic group, ventral division; caudal linear nucleus; caudate nucleus; compact portion of locus coeruleus; decussation of the superior cerebellar peduncle; diffuse portion of locus coeruleus; dorsal raphe nucleus, dorsal division; dorsal raphe nucleus, interfascicular division; dorsal raphe nucleus, lateral division; dorsal raphe nucleus, peripheral division; dorsal raphe nucleus, ventral division; dorsal thalamus; f; fornix; fourth ventricle; globus pallidus; hippocampus; hypothalamus; ic; internal capsule; main cluster of orexinergic neurons; medial habenular nucleus; medial longitudinal fasciculus; mlf; nucleus subcoeruleus, diffuse portion; optic tract; optic tract cluster of orexinergic neurons; paraventricular nuclei of the epithalamus; raphe magnus nucleus; rostral ventrolateral serotonergic group; scp; superior cerebellar peduncle; thalamic reticular nucleus; third ventricle; xscp; zi; zona incerta; zona incerta cluster of orexinergic neurons