Structural characteristics of neurons and macrogliocytes in interconnected regions of the mesoaccumbocingulate dopaminergic system in rats.

Studies in rats (n = 6) in normal conditions addressed the morphometric parameters of neurons and macrogliocytes in the interconnected anteromedial regions of the mesoaccumbocingulate (MAC) dopaminergic system, which is important for diagnosing and identifying the morphogenesis of addiction states. A spatial model of the system was constructed which took into account the mean distance of frontal sections from the frontal pole; the densities of neurons and macrogliocytes were assessed in the central part of the paranigral nucleus of the ventral tegmental area (VTA) and the compact zone of the substantia nigra (SN) and in the interconnected anteromedial segments of these midbrain nuclei, the cingulate fields, the nucleus accumbens (NA), and layer VI of the pregenual (Cg3) and layer III of the supragenual (Cg2) cingulate fields. The anteromedial segments of the paranigral nucleus of the VTA and the compact zone of the SN, which are interconnected with these cingulate structures and the NA, contained larger numbers of neurons than the other segments, as they occupied a larger volume, while there were no differences in the volumes of neurons in the anterior and central parts of these segments. The anterior part of the compact zone of the SN also differed in having a greater neuron density. The anteromedial parts of the paranigral nucleus of the VTA and the compact zone of the SN (12.20 +/- 0.10 mm from the frontal pole) had the greatest diagnostic value in the morphological assessment of addiction because the lateral part of the paranigral nucleus of the VTA contained the largest number of non-dopaminergic neurons, while the neuron bodies of the other nuclear groups of the VTA were small in size. The medial part of the NA had its greatest volume (and, thus, number of neurons) in the central part of the nucleus (5.10 +/- 0.10 mm from the frontal pole) at the level of the anterior part of the supragenual cingulate field (Cg2). Layer VI of the pregenual cingulate field (Cg3) was most compact at the level of the base of the anterior forceps (2.40 +/- 0.10 mm from the frontal pole).