Organization of the ascending projections from the ventral tegmental area: A multiple fluorescent retrograde tracer study in the rat

Abstract

The projections from the ventral tegmental area of Tsai (VTA) to the frontal cortex (FC), lateral septum (LS), were investigated in the rat by means of the double retrograde fluorescent tracer technique. True blue and fast blue were used in combination with nuclear yellow as retrograde tracers. After combined injections placed into two different terminal fields, many singly and some doubly labeled neurons were seen in the midbrain. In all cases the labeled cells were observed in the ipsilateral VTA, while after injections placed into the LS and Acc some fluorescent neurons were also seen in the contralateral VTA. The patterns of distribution of the labeled neurons showed a topographic organization of the VTA efferent pathways. However, some degree of overlapping was evident in the distribution of cells retrogradely labeled from different terminal fields. The number of the doubly labeled neurons varied according to the sites of combined injections, but in each experiment it never exceeded 10% of the total number of labeled perikarya. Doubly labeled neurons were particularly numerous after combined injections placed into the FC, LS, or LH; on the contrary, very few doubly labeled cells were observed after combined injections placed into the CPu and LS or LH. The organization of the ascending VTA projections suggests that they are probably integrated into different anatomical sets.

Ventral pallidum self-stimulation induces stimulus dependent increase in c-fos expression in reward-related brain regions

“…Alternatively, contralateral Fos expression may have been induced polysynaptically via VTA fibres known to traverse frontally to the other hemisphere. 1,5,8,43 Passive HF stimulation elicited a somewhat higher Fos-like activity than that obtained from animals which self-stimulated at the same average rate using equivalent pulse frequency. This finding implies that variables other than strength and average rate of stimulation contributed to the magnitude of Foslike immunoreactivity in the passively-stimulated group.…”

Properties and Opioid Inhibition of Mesolimbic Dopamine Neurons Vary according to Target Location

“…Identification and anatomical location of BLA-and NAc-projecting VTA DA neurons Dopaminergic projections from the VTA are organized into the mesolimbic and mesocortical systems, with the mesolimbic system sending major projections to both the BLA and the NAc (Albanese and Minciacchi, 1983;Le Moal and Simon, 1991;Brinley-Reed and McDonald, 1999;Hasue and Shammah-Lagnado, 2002). By using fluorescent microspheres as the retrograde tracer, we accurately identified only those VTA neurons that projected to these nuclei.…”

“…The mesolimbic dopamine (DA) system originates from neurons within the ventral tegmental area (VTA) and projects to limbic structures that include the nucleus accumbens (NAc) and the basolateral amygdala (BLA) (Albanese and Minciacchi, 1983). Dopamine projections to these target areas mediate both natural rewards and the rewarding aspects of drugs of abuse (Koob, 1992;White, 1996;Wise, 1996a,b).…”

Excitation of Ventral Tegmental Area Dopaminergic and Nondopaminergic Neurons by Orexins/Hypocretins

“…A10 dopamine neurons project from the VTA to the nucleus accumbens, amygdala, hippocampus, and prefrontal cortex, forming the mesocorticolimbic dopamine system (Albanese and Minciacchi, 1983). VTA GABAergic neurons also project to the prefrontal cortex and regulate the activity of VTA dopamine neurons via local axon collaterals (Steffensen et al, 1998).…”