A common system of sparsely-branched projection (reticular) NADPH-diaphorase neurons in formations of densely-branched cells in the human forebrain.

Morphometric studies of human forebrain formations composed of densely branched cells - the entorhinal cortex, the basolateral amygdala, the nucleus accumbens, the striatum, and the dorsal thalamus - were performed using nine parameters, with statistical analysis of the resulting data; measurements addressed the major projection-type densely branched and sparsely branched reticular neurons (scattered reticular and marginal reticular cells of the dorsal thalamus) stained by the Golgi method and with NADPH-diaphorase. Scattered reticular cells in the various formations showed no differences in any of the nine measures, while there were significant differences (in 5-7 measures, apart from one comparison, where there were differences in two measures) in their major projection-type densely branched cells. Scattered reticular and main projection-type densely branched neurons in each formation differed in terms of 7-9 measures. In endbrain formations, scattered reticular neurons contained NADPH-diaphorase; in the dorsal thalamus, only intermediate marginal reticular neurons were NADPH-diaphorase-positive. Thus, these human formations contained a common system of ancient integrative NADPH-diaphorase-containing reticular cells. Our results, along with published data, show these to be projection-type cells with projections to layers V and VI of the neocortex, which suggests that they have modulatory influences on its descending systems.

Neurons of the basal ganglia of the human brain (striatum and basolateral amygdala) expressing the enzyme NADPH-d.

Types of NADPH-d+ neurons (Vincent et al., 1983) were identified in the striatum and basolateral nuclei of the amygdala; striocortical neurons were detected in the striatum using the DiI marker (Belichenko and Dahlström, 1995). NADPH-d+ cells were numerous. Staining of these cells and all their processes, along with our previous studies of the neurons in these formations in the human brain using the Golgi method, allowed us to identify their shapes and identify them as sparsely or extensively branched cells. The main efferent neurons of the striatum and basolateral amygdala (extensively branched medium spiny cells and bushy spiny cells respectively) and their extensively branched interneurons did not contain NADPH-d. Efferent NADPH-d+ neurons included reticular, sparsely branched cells with long dendrites, which were the most numerous cells in both formations, as well as occasional large multipolar branched neurons; the striatum also contained numerous sparsely branched short-dendrite cells (a neuron type most represented in the brainstem and especially the reticular formation). Projections of reticular cells from the striatum to the cortex were demonstrated. NADPH-d+ interneurons were sparsely branched: in the striatum, these were slender, long-dendrite, bipolar cells (numerous), ordinary bipolar cells, twisted and large dendrite-poor cells; the amygdala contained the same bipolar cells along with radial neurons. Thus, NADPH-d+ neurons in these formations were more ancient, i.e., structurally less complex, cell types.

The role of the substantia nigra in cognitive activity in cats.

The role of the substantia nigra in cognitive processes of different levels of complexity was studied using an original method. Neurosurgical or neurochemical exclusion of the substantia nigra in cats led to significant impairment of conditioned reflex activity, generalization and abstraction processes; these recovered with pharmacological treatment directed to the dopaminergic system, with partial recovery after treatment directed to the GABAergic and cholinergic systems. Treatment directed to the serotoninergic system was ineffective.