The organization of monoamine neurons within the brainstem of the north american opossum (didelphis virginiana)

Abstract

The distribution of monoamine-containing neurons within the brain of the opossum is described using the Falck-Hillarp histofluorescence technique. Catecholamine-containing neurons are organized into four groups. The medulla contains one group which is located dorsolateral to the lateral reticular nucleus and ventrolateral to the dorsal vagal nucleus. The second collection is found within the pons and includes both the locus coeruleus and a region continuous with it referred to as the nucleus coeruleus, pars a . The third aggregate includes the substantia nigra, the ventral tegmental area, and the mesencephalic reticular formation and a fourth group is located within the periventricular and dorsal paraventricular nuclei of the hypothalamus. The indoleamine-containing cell bodies are distributed within the nuclei raphe obscurus, pallidus, magnus, dorsalis, and the nuclei linearis and superior centralis except a t certain pontine levels where they appear laterally within the reticular formation. A number of small intensely fluorescent @IF) cells are present within the connective tissue surrounding the brain and its blood vessels as well. Although certain differences are present, the distribution of monoamine neurons in the American opossum conforms generally to that described for the placental mammals studied to date.The Falck-Hillarp histochemical technique for visualizing biogenic amines (Carlsson e t al., '62; Falck, '62; Falck e t al., '62) provides a powerful tool for bridging the narrowing gap between the anatomy and chemistry of the nervous system. This comparatively simple procedure has already been utilized to map specific monoamine systems in the brain of the rat (Dahlstrom and Fuxe, '64; Jacobowitz and Palkovits, '74; Palkovits and Jacobowitz, '74), cat (Chu and Bloom, '74; Jones and Moore, '74; Pin e t al., '68; Maeda e t al., ' marsupial, has maintained a certain popularity for neuroanatomical research, not only for its significance from a comparative point of view, but also for its early availability in a n external pouch, providing a unique opportunity for developmental studies (Martin e t al., '75). The distribution of monoamine neurons in the opossum brain was studied and the results are described herein. To our knowledge, this is the first such description for any representative of the marsupial radiation. Spectrophotofluorometric analysis supports the generalization t h a t t h e green and orangeyellow fluorescence, induced by exposure to formaldehyde vapors, represent catecholamine (CAI and indoleamine (IA) fluorophors respectively (Corrodi and Jonsson, '67). Although such a designation will be followed in this paper, i t should be noted t h a t there is a n overlap in the spectral characteristics of the fluorophors depending on their concentration (Laszlo, '75). No attempt was made in this study to distinguish between the fluorescence of dopamine and norepinephrine since both of them exhibit a green fluorescence with this technique (Falck et al., '62).The original description of monoamin...

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

“…Although the RVL and CVL were continuous in the species studied, and indeed several other eutherian mammals previously studied (e.g. Maseko et al, 2007;Moon et al, 2007;Dwarika et al, 2008;Dell et al, 2010;Kruger et al, 2012), we distinguish two components of these ventrolateral columns, as the caudal portions have not been reported in the opossum or the monotremes (Crutcher and Humbertson, 1978;Manger et al, 2002b). The 5HT+ neurons forming the RPa nucleus were found in the ventral midline of the medulla associated with the pyramidal tracts.…”

Distribution and morphology of putative catecholaminergic and serotonergic neurons in the medulla oblongata of a sub-adult giraffe, Giraffa camelopardalis

“…The CVL 5HT column appears to be absent in the monotremes (Manger et al, 2002b), and the Virginia oppossum (Crutcher and Humbertson, 1978), but is present in the wallaby (Ferguson et al, 1999). The one difference in the giraffe studied is that the RVL 5HT column appeared to be more extensive anteriorly than that seen in other mammals.…”

The paleocerebellum and the integration of behavioral function

“…These ascending catecholamine neurons, constituting major portions of the dorsal noradrenergic pathway and the mesolimbic dopaminergic pathway, project to widespread areas of the limbic system and basal forebrain (Crutcher & Humbertson, 1978;Jacobowitz & MacLean, 1978;Lindvall & Bjorklund, 1974;Ungerstedt, 1971b) and have been heavily implicated in the regulation of many aspects of motivated behavior, including aggression (Reis, 1974;Welch & Welch, 1971), feeding and drinking (Ahlskog & Hoebel, 1973;Leibowitz, 1976;Ungerstedt, 1970Ungerstedt, , 1971a, and reinforcement processes (German & Bowden, 1974;Wise, 1978). Norepinephrine-containing neurons of the locus coeruleus also project back onto paleocerebellar structures, establishing a reciprocal feedback interaction with the anterior vermis and fastigial nucleus (Chu & Bloom, 1974;Snider, 1975).…”