Hippocampus subiculum

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. 

The hippocampal region comprises area dentata, hippocampus, subiculum, presubiculum, area retrosplenialis, parasubiculum and area entorhinalis. In this paper only the two former parts are dealt with. For nomenclature see Blackstad (1956). 

The hippocampus, which got its name from the Greek word for seahorse, due to its form, is a nucleus in the depth of the temporal lobe. The hippocampus is important for the integration of sensory information, for spatial orientation and for memory formation. The hippocampal formation contains the CA (cornu ammonis) regions, the dentate gyms and the subiculum. 

Moreover, all cells are not equally targeted in Alzheimer s disease, a disease that has discernable effects on consciousness (Perry et al., 1999). Large pyramidal cells of the frontal and temporal cortex, as well as the large pyramidal cells in CAl of hippocampus and subiculum, are the most susceptible to develop neurofibrillary tangles, to become dysfunctional and ultimately to die (Mann, 1996). It is the accumulation of abnormally hyperphosphorylated tau that disrupts the microtubular system of pyramidal cells in cortex and hippocampus both in experimental animal models and in Alzheimer s disease brain (Gong et al., 2000). 

Explicit memory depends upon die temporal lobe of die midbrain, an area tiiat includes the hippocampus and die nearby subiculum and entorhinal cortex.966 968-971 Implicit associative learning and memory involve die cerebellum, amygdala, and other regions.972 9723... 

Fig. 4 Staining for NeuN in hippocampus sector of control, day-4, day-9, and day-44 monkeys. Note the marked reduction of positive cells in CA1 contrasting the overall normal appearance of the other sectors. Cell loss in CA4 is shown by arrows, while the SVZi adjacent to CA1 is depicted by arrowheads. Asterisks, DG S, subiculum. Scale bar= 1 mm (D)...

The hippocampal formation includes DG, the hippocampus proper including CA1 -CA4 sectors (Lorente de No 1934) and the subiculum (van Hoesen 1982). Based on previous publications on postischemic cell proliferation in the rodent brain (e.g., Liu et al. 1998 Nakatomi et al. 2002), at first we focused our attention on DG and hippocampus proper. 

Unusually high levels of dysbindin-1 are found in neuronal and neuropil components of this brain area, which consists of the dentate gyrus (DG), hippocampus proper (i.e., cornu ammonis [CA] fields 1-3]), and the subiculum ( Figures 2.2-13c—d and O 2.2-14V). As in the case of the basal ganglia, an anatomical introduction clarifies the functional implications of dysbindin-1 found in the hippocampal formation ( Figures 2.2-13-2.2-18). For a detailed review of its anatomy, see Amaral and Lavenex (2007). 

Galani R, Weiss I, Cassel J-C, Kelche C. 1998. Spatial memory, habituation, and reactions to spatial and nonspatial changes in rats with selective lesions of the hippocampus, the entorhinal cortex or the subiculum. Behav Brain Res 96 1-12. 

In the hippocampus, D2 receptor binding is present in the stratum lacunosum molecolare and all layers of subiculum (Mansour et al., 1990 Levey et al., 1993 Yokoyama et al., 1994). In the presubiculum D2 receptor is expressed in layer II, whereas the parasubiculum does not contain D2 receptor. Lower levels of D2 receptor are present in the CA1 field, and in the piriform, entorhinal and perirhinal cortices. In the entorhinal cortex, layers I and III exhibit the highest density of D2 receptor, whereas in the perirhinal cortex a trilaminar pattern of D2 receptor is observed, with the highest levels in the external and deep laminae (Goldsmith and Joyce, 1994). 

In the human hippocampus, the highest binding was found in the molecular layer of the dentate gyrus and subiculum, whereas the binding was lower in CA3 and CA1, and no binding was found in the entorhinal cortex a trilaminar pattern of D2 receptor was instead observed in the perirhinal cortex (Goldsmith and Joyce, 1994). 

Figure 6.1. Schematic drawing by Ramon y Cajal (1911) of tire main cells, connections and flow of impulse traffic in tlie hippocampus. Alv alvus, CA Cornu Ammonis, DG dentate gyi us, EC entorhinal cortex, MF mossy fibers, PP perforant patli, Sch C ffer collaterals. Sub subiculum...

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