Connections of the nucleus accumbens

Reports from previous works has given different classifications for the nucleus accumbens. There also appears to be a general lack of information regarding the fiber connections of the nucleus. The present investigation was undertaken to clarify the connections of this structure. Silver impregnation methods were used to discern some of the afferent fibers of the nucleus, and autoradiographic techniques were used to locate target areas of efferent projections. Afferents were found to be predominately from the septum. Other sources of possible afferents were the mid cingulate gyrus and the ventral nucleus of the diagonal band. No argyrophilia was observed in the nucleus accumbens following transection of the fornix body, lesions of the anterior orbital frontal cortex or anterior cingulate gyrus. On the basis of grain counts made from autoradiographic studies, the nucleus accumbens projects predominately to the lateral hypothalamus. Counts above background were found in the cingulate gyrus, septum, ventral nucleus of the diagonal band, midline thalamic nuclei, habenula, caudate and substantia nigra. Thus, efferent projections appear to distribute to both limbic and extrapyramidal structures. Considering these connections and the functions reported by various workers the nucleus accumbens may serve as bridge between limbic and extrapyramidal motor systems effecting limbic influence in some movements.     

Distributions of periventricular projections of the paraventricular nucleus to the median eminence and arcuate nucleus

Neuronal projections from the periventricular subnucleus of the hypothalamic paraventricular nucleus to the median eminence and the arcuate nucleus were investigated in the rat by the anterograde tract-tracer, Phaseolus vulgaris leucoagglutinin. The vast majority of labeled fibers coursed ventrally along the third ventricle and distributed in the external layer of the median eminence bilaterally, with ipsilateral predominance moving caudalwards. Periventricular fibers also terminated in the arcuate nucleus, but this innervation was exclusively ipsilateral.     

Projections from the lateral mammillary nucleus to the anterodorsal thalamic nucleus in the rat

There has been an abundance of research on the connections of the mammillary bodies but the projections from the lateral mammillary nucleus to the anterodorsal thalamic nucleus has remained a gray area due to a dearth of material which directly addresses the details of this pathway. This study seeks to further define the nature of this particular nerve connection within the mammillothalmic tract. The technique employed is fluorescent nerve tract tracing using two fluorescent tracers implanted separately into each anterodorsal thalamic nucleus then followed retrogradely to the soma of the neurons in the lateral mammillary nucleus. Fluorescent photomicrography allowed us to document the single and double labeled cells of the lateral mammillary nucleus. The single labeled cells can be categorized into ipsilaterally projecting neurons and contralaterally projecting neurons. About half of all labeled cells were bilaterally projecting double-labeled, a third was ipsilaterally projecting single-labeled and the remainder were contralaterally projecting single labeled-cells. There were no labeled cells traced to the medial mamillary nucleus. The mammillary bodies play an important role in the limbic circuitry and a part of the so-called "Papez Circuit". The pathway by which the mammillary body projects to the other structures of the limbic system and the way it connects the limbic system to other parts of the brain like the tegmentum is not fully understood. This clarification of the connection between the lateral mammilary nucleus and the anterodorsal thalamic nucleus is but one of the contemplated pathways.     

Vestibular nucleus projections to nucleus tractus solitarius and the dorsal motor nucleus of the vagus nerve: potential substrates for vestibulo-autonomic interactions

Autonomic effects of vestibular stimulation are important components of phenomena as diverse as acute vestibular dysfunction and motion sickness. However, the organization of neural circuits mediating these responses is poorly understood. This study presents evidence for direct vestibular nucleus projections to brain stem regions that mediate autonomic function. One group of albino rabbits received injections of Phaseolus vulgaris leucoagglutinin into the vestibular nuclei. The tracer was visualized immunocytochemically with standard techniques. Anterogradely labeled axons from the caudal medial vestibular nucleus (cMVN) and inferior vestibular nucleus (IVN) could be traced bilaterally to nucleus tractus solitarius (NTS). Fewer axons ended near the somata of neurons in the dorsal motor nucleus of the vagus nerve (DMX). A second group of rabbits received pressure or iontophoretic injections of cholera toxin B-HRP or Fluoro-Gold into a region including NTS and DMX. Retrogradely labeled neurons were observed bilaterally in the caudal half of cMVN and ipsilaterally in IVN. The labeled somata were small and they tended to occupy the center of cMVN in transverse sections. These previously unreported vestibular nucleus projections to NTS and DMX are a potential substrate for vestibular influences on autonomic function. In particular, they may contribute to both cardiovascular control during head movements (e.g., orthostatic reflexes) and autonomic manifestions of vestibular dysfunction, motion sickness and exposure to altered gravitational environments.     

Chromosome structure inside the nucleus

Recent in situ three-dimensional structural studies have provided a new model for the 30 nm chromatin fiber. In addition, research during the past year has revealed some of the molecular complexity of non-histone chromosomal proteins. Still to come is the unification of molecular insights with chromosomal architecture.     

Ethanol inhibits single-unit responses in the nucleus accumbens evoked by stimulation of the basolateral nucleus of the amygdala

We studied the actions of intoxicating doses of ethanol on excitatory inputs from the basolateral nucleus of the amygdala, a major afferent system projecting to the nucleus accumbens (NAcc). In view of the hypothesized role of opioid receptors on the effects of ethanol on NAcc physiology, we also explored whether naloxone modulates ethanol-induced suppression of NAcc excitability in halothane anesthetized and freely moving unanesthetized rats. Intraperitoneal administration of ethanol (1.2-1.4 g/kg) markedly suppressed a subgroup of amygdala-activated NAcc neurons. The ethanol-induced reduction in amygdala-activated NAcc neurons was not reversed by naloxone (5.0 mg/kg, intraperitoneally). Moreover, naloxone had no effect on the suppressive effects of ethanol on NAcc spontaneous activity in either halothane-anesthetized or unanesthetized freely moving preparations. These findings suggest that opiate mechanisms either are not participating or are not solely responsible for the inhibitory effects of acute intoxicating doses of ethanol on NAcc physiology.     

Vestibular nucleus neurons, projecting to the "gastric" area of the solitary tract nucleus

OBJECTIVES: To describe the natural recovery of visuospatial neglect in stroke patients and the distribution of errors made on cancellation tests using a standardised neuropsychological test battery. METHOD: A prospective study of acute (< seven days) patients with right hemispheric stroke. Patients identified with visuospatial neglect were followed up for three months with monthly clinical and neuropsychological testing RESULTS: There were 66 patients with acute right hemispheric stroke assessed of whom 27 (40.9%) had evidence of visuospatial neglect. Patients with neglect, on admission, had a mean behavioural inattention test (BIT) score of 56.3, range 10-126 (normal>129). Three of the subtests identified errors being made in both the right and left hemispaces. During follow up, recovery occurred across both hemispaces, maximal in the right hemispace. Recovery from visuospatial neglect was associated with improvement in function as assessed by the Barthel score. At the end of the study period only six (31.5%) patients had persisting evidence of neglect. On admission the best predictor of recovery of visuospatial neglect was the line cancellation test (Spearman's rank correlation r=-0.4217, p=0.028). CONCLUSION: The demonstration of errors in both hemispaces has implications for the theory that neglect is a lateralised attentional problem and is important to recognise in planning the rehabilitation of stroke patients.     

Organization of the disynaptic pathway from the anteroventral cochlear nucleus to the lateral superior olivary nucleus in the ferret

The medial nucleus of the trapezoid body (MNTB) is one of three major nuclei of the superior olivary complex and provides an important inhibitory input from the contralateral ear to the lateral superior olivary nucleus (LSO) in the initial binaural pathway for coding interaural intensity differences. The major input to the MNTB from the contralateral anteroventral cochlear nucleus (AVCN) involves giant, calyx-like endings that have a one-to-one relationship with cells in the MNTB as confirmed in the ferret in this study. The main objective of the present study was to define the subsequent organization of projections from cells receiving these calyx-like endings. Several anatomical tracers (Phaseolus vulgaris leucoagglutinin, dextran-biotin, and biocytin) were used that are transported both anterogradely and retrogradely within neuronal projections in order to define the organization of MNTB connections with the LSO in the adult ferret. Analysis focused on determining the topography in both the transverse and longitudinal planes of the projections. Focal tracer injections in the LSO resulted in retrograde labeling of a long, narrow column of cells in the MNTB. The orientation and location of labeled cells was dependent on the medial-lateral position of the injection site. In the rostral-caudal dimension of MNTB, there was no such topographic relation between the injection site and the position of labeled cells. Labeled cells in the MNTB were distributed more or less evenly in a longitudinal column regardless of whether the injection site was restricted to the rostral, middle or caudal part of the LSO. In keeping with this pattern, tracer injections in the MNTB resulted in bands of labeled axons that distributed endings throughout the rostral-caudal axis of the LSO. These bands or sheets varied in medial-lateral position relative to the location of the injection site, but lacked any such rostral-caudal gradient. Thus, overall the MNTB-LSO projections have a convergent-divergent pattern of organization. While MNTB cells receive singular calyx-like endings from the AVCN, LSO cells receive projections from a long column of cells in the MNTB. Implications for processing interaural intensity differences are discussed.     

Synaptic integration of functionally diverse pallidal information in the entopeduncular nucleus and subthalamic nucleus in the rat

To determine the principles of synaptic innervation of neurons in the entopeduncular nucleus and subthalamic nucleus by neurons of functionally distinct regions of the pallidal complex, double anterograde labeling was carried out at both light and electron microscopic levels in the rat. Deposits of the anterograde tracers Phaseolus vulgaris-leucoagglutinin and biotinylated dextran amine were placed in different functional domains of the pallidal complex in the same animals. The tracer deposits in the ventral pallidum and the globus pallidus gave rise to GABA-immunopositive projections to the entopeduncular nucleus, the subthalamic nucleus, and the more medial lateral hypothalamus that were largely segregated but overlapped at the interface between the two fields of projection. In these regions the proximal parts of individual neurons in the entopeduncular nucleus, lateral hypothalamus, and subthalamic nucleus received synaptic input from terminals derived from both the ventral pallidum and the globus pallidus. Furthermore, the analysis of the afferent synaptic input to the dendrites of neurons in the subthalamic nucleus that cross functional boundaries of the nucleus defined by the pallidal inputs, revealed that terminals with the morphological and neurochemical characteristics of those derived from the pallidal complex make synaptic contact with all parts of the dendritic tree, including distal regions. It is concluded that functionally diverse information carried by the descending projections of the pallidal complex is synaptically integrated by neurons of the entopeduncular nucleus, lateral hypothalamus, and subthalamic nucleus by two mechanisms. First, neurons located at the interface between functionally distinct, but topographically adjacent, projections could integrate diverse information by means of the synaptic convergence at the level of the cell body and proximal dendrites. Second, because the distal dendrites of neurons in the subthalamic nucleus receive input from the pallidum, those that extend across two distinct domains of pallidal input could also provide the morphological basis of integration.     

Ultrastructure and distribution of axon terminals from the reticular thalamic nucleus to the anteroventral thalamic nucleus of the rat

The Bard Atherectomy Catheter is a new rotational atherectomy device that consists of a flexible, hollow, thin-walled cutting catheter that, while rotated at 1,500 revolutions per minute, is advanced across the lesion over a special spiral guidewire system. We report the initial clinical experience with this device in 20 peripheral lesions in ten patients. The majority of patients were treated for limb salvage. All lesions were successfully intervened on by atherectomy followed by adjunctive balloon angioplasty. A reduction to less than 50% stenosis was achieved in 13 of the 20 lesions (65%) after atherectomy but in all 20 lesions (100%) after adjunctive angioplasty for all lesions and stenting for dissections in two. Baseline minimal lesion lumen diameter was 0.8 +/- 0.7 mm with a reference vessel diameter of 4.2 +/- 1.7 mm (75 +/- 21% stenosis). The lumen improved to 2.0 +/- 0.8 mm (45 +/- 19% stenosis) (P < 0.001) following atherectomy and to 3.9 +/- 1.9 mm (13 +/- 16% stenosis) (P < 0.001) after adjunctive angioplasty. The average weight of removed atheroma was 45 +/- 58 mg. All ten patients had initial improvement in symptoms. At 6 months follow-up there was persistent improvement in eight patients and two subjects had undergone amputations. Our early clinical experience with this low profile, flexible atherectomy device, that enables extraction of a large amount of atheroma, suggests that it will become a valuable addition to current atherectomy technologies in small- and medium-sized vessels. The value of this device in coronary vessels is under investigation.     

Oxytocinergic inputs to the nucleus of the solitary tract and dorsal motor nucleus of the vagus in neonatal rats

BACKGROUND: Cetirizine is a H1 histamine antagonist which possesses anti-inflammatory properties through inhibition of leucocyte recruitment and activation, and reduction of ICAM-1 expression on mucosal epithelial cells. No studies have addressed the potential anti-inflammatory activities of cetirizine on skin keratinocytes. OBJECTIVES: Cetirizine and hydrocortisone were compared in their capacity to counteract human keratinocytes activation by IFNgamma. In particular, expression of immuno-modulatory membrane molecules and chemokine release have been examined. METHODS: Keratinocyte cultures established from normal skin of healthy donors were activated by IFNgamma (100-500 U/mL) in the absence or presence of cetirizine (10(-3)-10(3) microM) or hydrocortisone (10(-3)-10(2) microM), and tested for expression of ICAM-1, HLA-DR, MHC class I and CD40 as well as for release of RANTES, IL-8, macrophage chemotactic protein-1 (MCP-1) and granulocyte macrophage-colony stimulating factor (GM-CSF). RESULTS: Cetirizine at high concentrations (10(2)-10(3) microM) markedly inhibited IFNgamma-induced expression of membrane ICAM-1, HLA-DR and up-regulation of MHC class I, but had no effect on CD40 expression. In contrast, hydrocortisone (10(2) microM) enhanced IFNgamma-induced membrane ICAM-1, reduced expression of HLA-DR and did not alter expression of MHC class I and CD40. Consistently, high doses of cetirizine decreased, whereas hydrocortisone increased, soluble ICAM-1 levels in the supernatants of IFNgamma-treated keratinocytes. The inhibiting and stimulating effects of cetirizine and hydrocortisone, respectively, on ICAM-1 expression were confirmed at the mRNA level by Northern blot analysis. Finally, cetirizine, but not hydrocortisone, inhibited the release of MCP-1 and RANTES from IFNgamma-stimulated keratinocytes. In contrast, hydrocortisone, but not cetirizine, reduced GM-CSF and IL-8 release. CONCLUSIONS: The results indicate that cetirizine has the capacity to block the IFNgamma-induced activation of keratinocytes, and thus can exert important regulatory effects on TH1 cell-mediated immune responses in the skin. The high doses required for evidencing these activities suggest the potential benefits of a topical use of cetirizine.     

Localization of prothymosin alpha in the nucleus

Age differences in processing resources seem salient to age-related declines in secondary (or "recent") memory. Community-dwelling adults (N = 90, ages 30-80) completed 4 memory tests: Wechsler Memory Scale-Revised (WMS-R) Logical Memory (LM), Cowboy Story (CS), WMS-R Visual Reproductions (VR), and Extended Complex Figure Test (ECFT; Fastenau, in press). Two space-capacity measures (WMS-R Digit Span and Visual Memory Span) and 4 processing speed measures (cancellation and mental-tracking tasks) assessed processing resources. A statistical control procedure was used to isolate retrieval efficiency and measures contributions of age and processing resources to retrieval. A negative relationship between age and retrieval efficiency emerged on all measures (p < .05). The age effect was reduced 60% on LM and CS when processing resources were controlled, eliminated for VR, and unchanged on ECFT. It is possible that visual-spatial retrieval requires fewer processing resources than does verbal retrieval.     

The mosaic nature of the eukaryotic nucleus

The phylogenies for each of the protein-coding genes from the Methanococcus jannaschii genome were surveyed to determine the history of the major groups of life. For each gene, homologous sequences from other archaea, eucarya, and Gram-positive and Gram-negative bacteria were collected and aligned, and a phylogeny was reconstructed with a maximum-likelihood algorithm. The majority of significant phylogenies favor the eucarya and the archaca as sister groups. A smaller, but still substantial, portion of these significant phylogenies favor an eucarya/Gram-negative clade. These results indicate that support for the early history of life is not unequivocal. A chimeric origin of eukaryotes or an ancient, massive horizontal transfer of genes from Gram-negative bacteria to eucarya can explain many of the observed phylogenies.     

Chemoarchitecture of the rat lateral septal nucleus

The organization of lateral septal connections has been re-examined with respect to its newly defined subdivisions, using anterograde (PHAL) and retrograde (fluorogold) axonal tracer methods. The results confirm that progressively more ventral transverse bands in the hippocampus (defined by the orientation of the trisynaptic circuit) innervate progressively more ventral, transversely oriented sheets in the lateral septum. In addition, hippocampal field CA3 projects selectively to the caudal part of the lateral septal nucleus, which occupies topologically lateral regions of the transverse sheets, whereas field CA1 and the subiculum project selectively to the rostral and ventral parts of the lateral septal nucleus, which occupy topologically medial regions of the transverse sheets. Finally, the evidence suggests that progressively more ventral hippocampal bands innervate progressively thicker lateral septal sheets. In contrast, ascending inputs to the lateral septum appear to define at least 20 vertically oriented bands or subdivisions arranged orthogonal to the hippocampal input (Risold, P.Y. and Swanson, L.W., Chemoarchitecture of the rat lateral septal nucleus, Brain Res. Rev., 24 (1997) 91-113). Hypothalamic nuclei forming parts of behavior-specific subsystems share bidirectional connections with specific subdivisions of the lateral septal nucleus (especially the rostral part), suggesting that specific domains in the hippocampus may influence specific hypothalamic behavioral systems. In contrast, the caudal part of the lateral septal nucleus projects to the lateral hypothalamus and to the supramammillary nucleus, which projects back to the hippocampus and receives its major inputs from brainstem cell groups thought to regulate behavioral state. The neural system mediating defensive behavior shows these features rather clearly, and what is known about its organization is discussed in some detail.     

Lectin staining in the basal nucleus (Meynert) and the hypothalamic tuberomamillary nucleus of the developing human prosencephalon

Previous studies have demonstrated that extracellular matrix glycoconjugates, shown by lectin-histochemistry with Vicia villosa agglutinin (VVA) and peanut agglutinin (PNA) as so-called perineuronal nets, play an important role in brain maturation. Concanavalin A (ConA) binding to neuronal surface glycoconjugates may be a marker of synaptic junctions. The present study was done to demonstrate the binding sites of these lectins in two functionally related nuclei of the prosencephalon, the basal nucleus (Meynert) and the hypothalamic tuberomamillary nucleus. Fetal brains of 16-36 weeks of gestation were examined by using VVA, PNA, and ConA to determine appearance and distribution patterns of specific lectin-binding sites on glycoconjugates during fetal brain development. The basal nucleus and the tuberomamillary nucleus showed a characteristic "cellular staining" that may have been due to cytoplasmatic labeling, surface labeling, or both. Lectin-staining occurred much earlier in the basal nucleus than in the tuberomamillary nucleus. Although all three lectins were bound to neurons of the basal nucleus, only ConA-positive neurons were observed in the tuberomamillary nucleus. In conclusion, lectin-labeled cells most probably represent projection neurons that are GABAergic (tuberomamillary nucleus) or cholinergic (basal nucleus). Labeling with the three lectins demonstrated nuclear-specific staining patterns that occur early in fetal development and gradually increase. Binding sites for lectins characterizing perineuronal nets (VVA, PNA) occurred only in the basal nucleus, whereas binding sites for ConA on neuronal-surface glycoconjugates, which seem to play a role in early synaptogenesis, were present in the basal and the tuberomamillary nucleus. The basal nucleus, however, expressed ConA binding sites distinctly earlier, probably indicating early arriving afferents.