Nuclear organisation of some immunohistochemically identifiable neural systems in three Afrotherian species—Potomogale velox, Amblysomus hottentotus and Petrodromus tetradactylus

Abstract

Paul.Manger@wits.ac.za 2 Highlights  The organisation of four neural systems is described in the brains of three Afrotherians not previously studied  These systems are organised in a similar manner to other mammals.  There are features that reflect both phylogenetic and functional signals in the evolution of these neural systems.  The golden mole appears to be a "hyper-cholinergic" mammal, possessing cholinergic neurons in novel regions of the brain. AbstractThe present study describes the organization of the cholinergic, catecholaminergic, serotonergic and orexinergic (hypocretinergic) neurons in the brains of the giant otter shrew, the Hottentot golden mole and the four-toed sengi, three members of the mammalian super orderAfrotheria. The aim of the present study was to investigate the possible differences in the nuclear complement of these neural systems in comparison to previous studies on other Afrotheria species and other mammalian species. Brains of the golden mole, sengi and giant otter shrew were coronally sectioned and immunohistochemically stained with antibodies against cholineacetyl-transferase, tyrosine hydroxylase, serotonin and orexin-A. The majority of nuclei revealed in the current study were similar between the species investigated, to other Afrotherian species investigated, and to other mammals, but certain differences in the nuclear complement highlighted phylogenetic interrelationships. The golden mole was seen to have cholinergic interneurons in the cerebral cortex, hippocampus, olfactory bulb and amygdala. The four-toed sengi had cholinergic neurons in both colliculi and in the cochlear nucleus, but lacked the catecholaminergic A15d group in the hypothalamus. In both the golden mole and the four-toed sengi, the locus coeruleus (A6d group) was made up of few neurons. The golden mole also exhibited an unusual foreshortening of the brain, such that a major kink in the brainstem was evident. The results of this study, framed in a phylogenetic context, appear to indicate that the golden mole and four-toed sengi share a more recent common ancestor that diverged from the tenrec lineage early in the phylogenetic history of the Afrotherians.

Nuclear organisation of some immunohistochemically identifiable neural systems in five species of insectivore —Crocidura cyanea, Crocidura olivieri, Sylvisorex ollula, Paraechinus aethiopicus and Atelerix frontalis

“…Overall, the nuclear organization and complement of the cholinergic system in the five insectivorous species studied was similar to all other mammals studied to date (Dell et al, 2010;Calvey et al, 2013). Two notable differences were the absence of the parabigeminal and Edinger-Westphal nuclei in the three shrew (Soricidae) species studied, although these nuclei were both present in the two hedgehog species studied.…”

“…The neurons forming the parabigeminal nucleus (PBg) were either not ChAT immunoreactive or absent in all three shrew species, but were present in the two hedgehog species. The neurons forming the Edinger-Westphal nucleus (EW) were not ChAT immunoreactive, or absent, in Crocidura 13 Table 1: Summary of the nuclei delineated in the current study of insectivores in comparison to similar studies previously undertaken in Afroinsectiphilia (Calvey et al, 2013), Erinaceidae Papadopoulos,1995, 1996 and current study), Soricidae (current study), Microchirotpera (Maseko and Manger, 2007,b;Kruger et al, 2010a,b) and Megachiroptera Dell et al, 2010Dell et al, , 2013. Cells with a dark grey background indicate order distinguishing features.…”

“…1, 2). The nomenclature used for the cholinergic nuclei was adopted from Woolf (1991), Limacher et al (2008), Bhagwandin et al (2008), Gravett et al (2009), Pieters et al (2010, and Calvey et al (2013), the catecholaminergic nuclei from Hökfelt et al (1984), Smeets and Gonzalez (2000), Limacher et al (2008), Bhagwandin et al (2008), Gravett et al (2009), Pieters et al (2010 and Calvey et al (2013), the serotonergic nuclei from Törk (1990), Limacher et al (2008), Bhagwandin et al (2008), Gravett et al (2009), Pieters et al (2010 and Calvey et al (2013), and the orexinergic nuclei from Kruger et al (2010b), Bhagwandin et al (2011), Gravett et al (2011 and Calvey et al (2013). …”

“…Within the left and right ventrolateral medullary tegmentum a distinct anteroposterior column of 5HT+ neurons of moderate density extending from the level of the facial nucleus to the spinomedullary junction were observed. These have previously been termed the rostral and caudal ventrolateral serotonergic columns (e.g., Moon et al, 2007;Dwarika et al, 2008;Calvey et al, 2013). The RVL began as a lateroventral continuation of 5HT+ neurons from the lower portion of the RMg extending over the pyramidal tracts and trapezoid body, and consolidating as a distinct column lateral to the inferior olivary nuclear complex.…”

“…In four out of the six microchiropterans Kruger et al, 2010a), the parabigeminal nucleus is also absent and the Edinger-Westphal nucleus was absent in one microchiropteran . In all other mammals, the parabigeminal and Edinger-Westphal nuclei are present (Dell et al, 2010;Calvey et al 2013), even in the microphthalmic mole rats and golden mole (Da Silva et al, 2006;Bhagwandin et al, 2008;Calvey et al, 2013). The laterodorsal tegmental nucleus, while present in all mammals studied to date (Dell et al, 2010), has shown some variance across species (e.g.…”