Neuroscience
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The beneficial effects of caffeine on cognition are controversial in humans, whereas its benefit in rodents had been well characterized. However, most studies were performed with acute administration of caffeine and the tasks used to evaluate cognition had aversive components. Here, we evaluated adulthood administration of caffeine up to old age on recognition memory in mice using the object recognition task (ORT) and on brain-derived neurotrophic factor (BNDF) and tyrosine kinase receptor (TrkB) immunocontent in the hippocampus. ⋯ Caffeine also counteracted the age-related increase in BDNF and TrkB immunocontent. Our results corroborate with other studies and reinforce that caffeine consumed in adulthood may prevent recognition memory decline with aging. This preventive effect may involve a decrease in the hippocampal BDNF and TrkB immunocontent.
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The mammalian cerebellum is composed of a highly reproducible array of transverse zones, each of which is subdivided into parasagittal stripes. By using a combination of Purkinje cell antigenic markers and afferent tracing, four transverse zones have been identified: the anterior zone (AZ: approximately lobules I-V), the central zone (CZ: approximately lobules VI-VII), the posterior zone (PZ: approximately lobules VIII-dorsal IX) and the nodular zone (NZ: approximately ventral lobule IX+lobule X). Neurofilament-associated antigen (NAA) is an epitope recognized by a monoclonal antibody, which is expressed strongly in association with neurofilaments. ⋯ The novel restriction boundary at lobule VII/VIII, which is also reflected in the morphology of the external granular layer and aligns with a gap in the developing Purkinje cell layer, precedes the morphological appearance of the posterior superior fissure between lobules VIb and VII. In addition, afferent axons to the CZ terminate in an array of parasagittal stripes that is probably a specific climbing fiber projection. Thus, the transverse zone architecture of the mouse cerebellum is more complex than had previously been appreciated.
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The activation of glial cells in the CNS has been suggested to be involved in abnormal pain sensation after peripheral nerve injury. Previous studies demonstrated phosphorylation of p38 mitogen-activated protein kinase (MAPK) in spinal cord glial cells after peripheral nerve injury, and such phosphorylation has been suggested to be involved in the development of neuropathic pain. The aim of this study was to examine the dorsal column nuclei for phosphorylation of p38 MAPK following peripheral nerve injury and to explore a possibility of its contribution to neuropathic pain. ⋯ Continuous infusion of a p38 MAPK inhibitor into the cisterna magna for 14 days beginning on the day of SNL suppressed the development of tactile allodynia, but not thermal hyperalgesia induced by nerve injury. These results demonstrate that SNL activates p38 MAPK pathway in microglia in the gracile nucleus as well as in the spinal cord dorsal horn. Activation of p38 MAPK in medullary microglia may contribute to the pathogenesis of neuropathic pain.
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The c-kit receptor tyrosine kinase is expressed in a subpopulation of small- and medium-sized neurons of the dorsal root ganglia (DRG) and in the superficial layer of the spinal cord. Stem cell factor (SCF), a ligand of the c-kit receptor, induces neurite outgrowth from DRG and supports the survival of c-kit-expressing neurons. To clarify the possible function of the SCF/c-kit receptor system in the adult animal, we investigated the expression of c-kit receptor in the spinal cord and DRG in relation to pain by using H2C7, a newly developed anti-c-kit monoclonal antibody. ⋯ Selective elimination of unmyelinated C-fibers by neonatal capsaicin treatment resulted in marked reduction of the c-kit receptor and CGRP expression in the superficial layer of the spinal cord. Cell-size profiles showed that c-kit receptor expression was significantly up-regulated and down-regulated in medium-sized DRG neurons after neonatal capsaicin treatment and nerve injury, respectively. These results suggest that the c-kit receptor is mainly expressed in peptidergic small-sized DRG neurons and may be involved in pain regulation both peripherally and centrally.
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The classification, morphology and function of enteric neurons have been extensively studied in the small and large intestine. However, little is known about enteric neurons that directly project to the CNS. Previous studies have identified these unique neurons in the rectum, rectospinal neurons, but little was done to characterize them. ⋯ The expression of the peptides and receptors suggests that there are at least two separate populations of neurons projecting from the colon to the CNS. The data suggest that these colospinal afferent neurons (CANs) might be involved in nociception. Whether sensory information from CANs is perceived by the animal or is part of the parasympathetic reflex is currently not known.