Efferent projections of the retrorubral nucleus to the substantia nigra and ventral tegmental area in cats as shown by anterograde tracing

Abstract

The aim of the present study was to determine whether the retrorubral nucleus projects to the dopaminergic nuclei in the ventral midbrain of the cat. For this purpose, injec tions of biotinylated dextran-amine or Phaseolus vulgaris-leucoagglutinin were placed into the retrorubral nucleus under ste reotaxic guidance. The tracers were visualized by means of (immune) histochemical procedures. In addition, tyrosine hy droxylase immunohistochemistry was used to evaluate the lo cation of the injection sites and the distribution of the anterogradely labeled fibers. Both tracers reveal the same topography of labeled fibers in the ventral mesencephalon. Labeled fibers with varicosities were found ipsilaterally in the substantia nigra pars compacta, the substantia nigra pars lateralis, the ventral tegmental area and, contralaterally, In the substantia nigra pars compacta* the ventral tegmental area, and the retrorubral nu cleus, A considerable number of labeled axons with varicosities were observed to be wrapped around the dendrites and perikarya of tyrosine hydroxylase-positive neurons in these areas. The present results are discussed in view of the possible role of the A8 dopaminergic cell group in the coordination of A9 nigrostriatal and A10 mesolimbic systems, as well as in the progres sive pathology seen In patients suffering from Parkinson's dis ease.KEY WORDS: A8, A9, A10, Dopamine, Tyrosine hydroxylase im munohistochemistry, Phaseolus vulgaris-leucoagglutinin, Bioti nylated dextran-amine.

Distribution of somatostatin-28 (1-12) immunoreactivity in the diencephalon and the brainstem of the dog

“…Somatostatin-positive perikarya have been found in the retrorubral area of the cat and the rat by some authors (Graybiel and Elde 1983;Vincent et al 1985) but not others (Johansson et al 1984;Spangler and Morley 1987). In the dog, labeled cells in this area overlap the ventral extension of the A8 dopaminergic neuronal group that have been suggested to play a key role in the progression of the Parkinson's disease (Arts et al 1996;Tafti et al 1997;García et al 1997). The dense population of labeled cells in the rostral part of the dorsal raphe nucleus of the dog closely resembles a similar population described in the rat (Johansson et al 1984).…”

The mesopontine rostromedial tegmental nucleus: A structure targeted by the lateral habenula that projects to the ventral tegmental area of Tsai and substantia nigra compacta

“…Among these, a particularly robust projection distributes bilaterally within the VTA/SNC complex (Figs. 10H–J and 11) with a density that far exceeds that of other mesopontine structures reported to innervate the dopaminergic districts (e.g., Deutch et al, 1988; Hallanger et al, 1988; Cornwall et al, 1990; Vertes et al, 1991; Arts et al, 1996; but see also Ferreira et al, 2008; see also Table 2). Alternatively, the RMTg-VTA/SNC projection appears to be not so much more dense than RMTg inputs to several other structures listed above that give rise to massive ascending “state-setting” projections (Mesulam, 1990; Aston-Jones et al, 1991; 2000), which include the nigral complex, pedunculopontine and laterodorsal tegmental nuclei and median and dorsal raphe nuclei (Anden et al, 1964; 1965; 1966; Fallon et al, 1978; Fallon and Moore, 1978; Lindvall and Björklund, 1983; Björklund and Lindvall, 1984; Swanson, 1982; Deutch et al, 1988; Hallanger and Wainer, 1988; Cornwall et al, 1990; Vertes, 1991; Vertes et al, 1999; Gritti et al, 1997; 2003).…”

An update on the connections of the ventral mesencephalic dopaminergic complex

“…In addition, the RRF projects to the VTA, SNc, and PAGvl (Deutch et al, 1988; Arts et al 1996; Zahm et al, 2011b). The PAGvl has intra-PAG associational connections and GABA (Kirouac et al, 2004) inputs from the VTA (Vianna and Brandao, 2003; Zahm et al, 2011b), GLU outputs to the VTA (Geisler et al, 2007), GABA outputs to the VTA contacting DA and GABA neurons (Omelchenko and Sesack, 2010), and outputs to the RRF of undetermined phenotype (Zahm et al, 2011b).…”

“…The issue of which outputs from these structures are DAergic is exacerbated by the substantial proportions of non-DA projection neurons in the RRF and PAGvl. The RRF projects to the olfactory tubercle, striatum, Acb, interstitial nucleus of the posterior anterior commissure, BST, amygdala, and pyriform and entorhinal cortices (Jimenez-Castellanos and Graybiel, 1987; Arts et al, 1996), but with particular density to EA structures (Deutch et al, 1988 Shammah-Lagnado et al, 1999; Hasue and Shammah-Lagnado, 2002). Outputs from the PAGvl terminate in the Acb, caudate putamen, medial prefrontal cortex, lateral septum, hippocampus, magnocellular basal forebrain, LHb, BST, and amygdala (Pohle et al, 1984; Descarries et al, 1986; Semba et al, 1988; Yoshida et al, 1989; Stratford and Wirtshafter, 1990; Li et al, 1993), but, again, most strongly in the EAc (Hasue and Shammah-Lagnado, 2002).…”