Distribution and morphology of putative catecholaminergic and serotonergic neurons in the medulla oblongata of a sub-adult giraffe, Giraffa camelopardalis N. Ludo Badlangana a , Adhil Bhagwandin a , Kjell Fuxe b , Paul R. Manger a, * a School of Anatomical Sciences, Faculty of Health Sciences, University of the Witwatersrand, 7 York Road, Parktown 2193, Johannesburg, Republic of South Africa b Department of Neuroscience, Karolinska Institutet, Retzius va ¨g 8, S-171 77 Stockholm, Sweden Received 19 March 2007; received in revised form 2 May 2007; accepted 2 May 2007 Available online 22 May 2007 Abstract The current study details the nuclear parcellation and appearance of putative catecholaminergic and serotonergic neurons within the medulla oblongata of a sub-adult giraffe, using immunohistochemistry for tyrosine hydroxylase and serotonin. We hypothesized that the unusual phenotype of the giraffe, this being the long neck and potential axonal lengthening of these neurons, may pose specific problems in terms of the efficient functioning of these systems, as several groups of catecholaminergic and serotonergic neurons, especially of the medulla, are known to project to the entire spinal cord. This specific challenge may lead to observable differences in the nuclear parcellation and morphology of these systems in the giraffe. Our personal observations in the giraffe reveal that, as with other Artiodactyls, the spinal cord extends to the caudal end of the sacral vertebrae. Within the giraffe medulla we found evidence for five putative catecholaminergic (neurons containing tyrosine hydroxylase) and five serotonergic nuclei. In terms of both morphological appearance of the neurons and nuclear parcellation we did not find any evidence for features that may be considered affected by the phenotype of the giraffe. The nuclear parcellation and appearance of both the putative catecholaminergic and serotonergic systems in the medulla of the giraffe studied are strikingly similar to that seen in previous studies of other Artiodactyls. We interpret these findings in terms of a growing literature detailing order specific phylogenetic constraints in the evolution of these neuromodulatory systems. # 2007 Elsevier B.V. All rights reserved. Keywords: Tyrosine hydroxylase; Serotonin; Evolution; Artiodactyl; Neural systems 1. Introduction The phenotypically unusual long neck of the giraffe (Giraffa camelopardalis), which can be well over 1 m long, presents a range of potential problems for a variety of neural systems. The spinal cord terminates at the sacral level and in itself can be over 1.5 m in length in sub-adult giraffe (personal observations). Furthermore, there are nerves that project to the viscera such as the vagus and phrenic nerves that presumably have significantly longer distances to cover than would be the case in other Artiodactyla and mammals. In this study, the catecholaminergic and serotonergic systems of the medulla of the giraffe were examined using immunohistochemistry for tyrosine hydro- xylase to reveal putative catecholaminergic neurons and serotonin to reveal serotonergic neurons. The specific nuclei forming the catecholaminergic systems normally observed in the medulla of mammals are the rostral www.elsevier.com/locate/jchemneu Journal of Chemical Neuroanatomy 34 (2007) 69–79 Abbreviations: 10, dorsal motor vagus nucleus; 12, hypoglossal nucleus; 12n, hypoglossal nerve; A1, caudal ventrolateral medullary tegmental group; A2, caudal dorsomedial medullary group; AP, area postrema; C1, rostral ventrolateral medullary tegmental group; C2, rostral dorsomedial medullary group; Cu, cuneate nucleus; CVL, caudal ventrolateral medullary tegmental serotonergic cell column; DC, dorsal cochlear nucleus; DMS, dorsomedial spinal trigeminal nucleus; ECu, external cuneate nucleus; flm, medial long- itudinal fasciculus; Ge5, gelatinous layer of the caudal spinal trigeminal nucleus; Gr, nucleus gracilis; icp, inferior cerebellar peduncle; io, inferior olive; LRt, lateral reticular nucleus; MdD, medullary reticular nucleus dorsal part; MdV, medullary reticular nucleus ventral part; N.Amb, nucleus ambiguus; oc, olivocerebellar tract; py, pyramidal tract; pyx, pyramidal decussation; RMg, raphe magnus nucleus; ROb, raphe obscurus nucleus; RPa, raphe pallidus nucleus; RVL, rostral ventrolateral medullary tegmental serotonergic cell column; Sp5, spinal trigeminal nucleus; Sp5c, spinal trigeminal nucleus caudal part; SpVe, spinal vestibular nucleus; vc, ventral cochlear nucleus; VII, facial nerve nucleus * Corresponding author. Tel.: +27 11 717 2497; fax: +27 11 717 2422. E-mail address: mangerpr@anatomy.wits.ac.za (P.R. Manger). 0891-0618/$ – see front matter # 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.jchemneu.2007.05.003