Lateral habenula

Double retrograde labeling of the VTA neurons from the frontal cortex, lateral septum, NAc, CPu and lateral habenula did not point out a highly divergent collateralization of VTA neurons (Albanese and Minciacchi, 1983). VTA neurons bifurcating to more than one target did not seem to exceed 10% of the total labeled population, and were relatively numerous when the injections were placed in the frontal cortex, lateral septum or lateral habenula (see also Section 8.2). 

As described in detail by Bjorklund and Lindvall (1984), the dopaminergic fibers form a dense plexus in the lateral habenular nucleus. This contingent of innervation is concentrated in the medial portion of the lateral habenula. Bjorklund and Lindvall (1984) pointed out that substantial evidence from lesion and tracing experiments had indicated that such DA innervation originates in the A10 cell group. In the retrograde... 

Interestingly, experimental chronic amphetamine and cocaine administration induces degeneration confined to the lateral habenula and its main output pathway, the fasciculus retroflexus (reviewed by Ellison, 1994). The habenula is the key relay in the descending dorsal diencephalic system, consisting of stria medullaris, habenula and fasciculus retroflexus, which links the limbic forebrain and the basal ganglia with lower diencephalic and mesencephalic centers (see for review Ellison, 1994). Dopaminergic dysfunction in this circuit could be implicated in psychiatric diseases including schizophrenia (Ellison, 1994). 

Medium-high density of D2 receptors was found in the islands of Calleja, ventral pallidum, zona incerta, GP, central amygdala, in some cells of the anterior lobe of the pituitary, and at several sites in the forebrain the laterodorsal septal area, hippocampus, subiculum, lateral habenula, STh, lateral mammillary bodies. D2 receptors were also found with a medium-high density in various cortical fields prefrontal, anterior cingulate, entorhinal and perirhinal cortices. In the brain stem, medium-high density of D2 receptors was found in the VTA, SNc, ventral SNr, parabrachial nucleus, superior and inferior colliculi, dorsal raphe nucleus and locus coeruleus. 

Medium-low density of D3 mRNA was found in the agranular insular, fronto-parietal, temporal and occipital cortices, in the hippocampal formation, amygdaloid complex, in thalamic nuclei (anteroventral, anterodorsal, laterodorsal, ventroposterolateral and centromedial nuclei), in the lateral habenula, CPu, STh, VTA, paraventricular and ventromedial hypothalamic nuclei, and superior colliculus (Bouthenet et al., 1991 Landwehrmeyer et al., 1993b Diaz et al., 1995, 2000). No receptor signal could be detected in the pituitary gland (Sokoloff et al., 1990). 

Except for the hilar region of the islands of Calleja, the lateral habenula and the Purkinje cells of cerebellum, D3 mRNA matched the distribution of the receptor (Diaz et al., 2000). In the archicerebellum, in fact, D3 mRNA was found to be expressed in the Purkinje cells of lobules 9 and 10, whereas D3 binding sites were contained in the molecular layer surrounding the Purkinje cell layer of lobule 10 and in the ventral molecular layer of lobule 9 (Levant et al., 1993 Diaz et al., 1995). 

Christoph GR, Leonzio RJ, Wilcox KS (1986) Stimulation of the lateral habenula inhibits dopamine-containing neurons in the substantia nigra and ventral tegmental area of the rat. / Neurosci., 6, 613-619. 

In situ hybridization. 5A, 5B and 7, Dark-field microscopy of the emulsion autoradiogram of horizontal section through an adult mouse brain, hybridized with either the 5-ht5, (5A), the S-htgQ (5B) [7], and the 5-ht, probe (7) [our unpublished data]. Cx, cerebral cortex H, hippocampus Cb, cerebellum CAl, CA2-3, hippocampal area MH, median habenula LH, lateral habenula LS, lateral septum, Ent, enthorhinal cortex. 

Caudate nucleus Frontal cortex Parietal cortex Globus pallidus Lateral habenula... 

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