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The caudomedial shell of the rat nucleus accumbens exhibits inhomogeneous distribution patterns of the vesicular glutamate transporters 1 (VGLUT1) and 2 (VGLUT2). This paper focuses on the question of whether patterns of VGLUT1 and VGLUT2 correspond to cytoarchitectonically and cytochemically defined subterritories of the caudomedial shell region. VGLUT2 was shown to be coexpressed with calretinin in the dense axonal plexus known to emanate from the paraventricular thalamic nucleus. In regions termed corridors, which are spared by this paraventricular thalamic innervation, axonal terminals were found to be clustered and VGLUT1-immunoreactive. It is assumed that these fibers originate in the prelimbic cortex and/or in the parvicellular basal amygdaloid nucleus known to project to accumbal shell components. Our findings confirm the existence of two well-separated neuronal circuits in the caudomedial shell that are dominated by two different excitatory input systems originating from either thalamic, cortical, or cortex-like amygdaloid sources. The large lateral corridors—which resemble the accumbal core not only in respect to their VGLUT1 immunolabeling but also concerning their content of calbindin-positive cells—may represent a component of the anatomically weakly defined accumbal shore region. J. Comp. Neurol. 465:1–10, 2003. © 2003 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

Recent reports suggest a far greater plasticity in nerve tissue than previously believed. As the digestive tract is exposed to a variety of insults, this question is relevant to enteric nerves, but little is known about their ability to recover from damage. To address this problem, we ablated the myenteric plexus of the mouse colon with the detergent benzalkonium chloride (BAC) and followed the ensuing morphologic changes for up to 60 days by using light- and electron microscopy. We found that, 2 days after BAC application, the treated area was essentially devoid of intact nerve elements. From day 7, new nerve fibers were observed within the denervated region. This growth progressed until, at days 30–60, newly grown nerve fibers were present in most of this region, and the pattern of muscle innervation was similar to the normal one. At least part of these fibers originated at neurons within intact ganglia surrounding the denervated region. The cross-sectional area of neurons near the denervated region at day 14 was 52% greater than controls. Glial cells were closely associated with the regenerating nerve fibers. From day 14 onward, we observed undifferentiated cells and differentiating neurons in ganglia surrounding the denervated region, and by day 30, new neurons were present in the myenteric region, along with regenerating nerve fibers. We conclude that the myenteric plexus is endowed with a considerable ability of regeneration and plasticity. The results provide evidence for the presence of stem cells and for an adult neurogenesis in this plexus. J. Comp. Neurol. 462:315–327, 2003. © 2003 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

Although the rabbit brain, in particular the basal forebrain cholinergic system, has become a common model for neuropathological changes associated with Alzheimer''s disease, detailed neuroanatomical studies on the morphological organization of basal forebrain cholinergic nuclei and on their output pathways are still awaited. Therefore, we performed quantitative choline acetyltransferase (ChAT) immunocytochemistry to localize major cholinergic nuclei and to determine the number of respective cholinergic neurons in the rabbit forebrain. The density of ChAT-immunoreactive terminals in layer V of distinct neocortical territories and in hippocampal subfields was also measured. Another cholinergic marker, the low-affinity neurotrophin receptor (p75NTR), was also employed to identify subsets of cholinergic neurons. Double-immunofluorescence labeling of ChAT and p75NTR, calbindin D-28k (CB), parvalbumin, calretinin, neuronal nitric oxide synthase (nNOS), tyrosine hydroxylase, or substance P was used to elucidate the neuroanatomical borders of cholinergic nuclei and to analyze the neurochemical complexity of cholinergic cell populations. Cholinergic projection neurons with heterogeneous densities were found in the medial septum, vertical and horizontal diagonal bands of Broca, ventral pallidum, and magnocellular nucleus basalis (MBN)/substantia innominata (SI) complex; cholinergic interneurons were observed in the caudate nucleus, putamen, accumbens nucleus, and olfactory tubercule, whereas the globus pallidus was devoid of cholinergic nerve cells. Cholinergic interneurons were frequently present in the hippocampus and to a lesser extent in cerebral cortex. Cholinergic projection neurons, except those localized in SI, abundantly expressed p75NTR, and a subset of cholinergic neurons in posterior MBN was immunoreactive for CB and nNOS. A strict laminar distribution pattern of cholinergic terminals was recorded both in the cerebral cortex and in CA1–CA3 and dentate gyrus of the hippocampus. In summary, the structural organization and chemoarchitecture of rabbit basal forebrain may be considered as a transition between that of rodents and that of primates. J. Comp. Neurol. 460:597–611, 2003. © 2003 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]