Brain research
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Afferent pathways innervating the urinary bladder consist of myelinated Adelta- and unmyelinated C-fibers, the neuronal cell bodies of which correspond to medium and small-sized cell populations of dorsal root ganglion (DRG) neurons, respectively. Since hyperpolarization-activated cyclic nucleotide-gated cation (HCN) channel currents have been identified in various peripheral sensory neurons, we examined the expression of isoforms of HCN channels in the L6-S1 spinal cord and bladder afferent neurons from L6-S1 DRG in rats. ⋯ In dye-labeled bladder afferent neurons, HCN-2-positive cells were found in approximately 60% of neurons, and HCN-2 was expressed in both small- and medium-sized neurons with a higher ratio (expression ratio: 61% and 50% of neurons, respectively) compared with unidentified DRG neurons, in which the HCN expression ratio was 47% and 21% of small- and medium-sized cells, respectively. These results suggest that HCN-2 is the predominant subtype of HCN channels, which can control neuronal excitability, in small-sized C-fiber and medium-sized Adelta fiber DRG neurons including bladder afferent neurons, and might modulate activity of bladder afferent pathways controlling the micturition reflex.
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Previous studies have demonstrated that either transplantation of bone marrow stromal cells (MSC) or physical exercise regimens can elicit limited functional recovery following spinal cord injury, presumably through different mechanisms. The present study examined whether transplantation of MSC derived from transgenic Fischer alkaline phosphatase (AP) rats, in combination with exercise, would have synergistic effects leading to recovery of function that is greater than either alone. Adult female Sprague-Dawley rats received a moderate thoracic contusion injury and were divided into three groups: operated controls (Op-Control), MSC transplant recipients (MSC), and MSC transplant recipients plus exercise (MSC+Ex). ⋯ Immunocytochemical analysis provided no evidence that MSC differentiated into neurons, astrocytes or oligodendrocytes. Muscle mass of the medial gastrocnemius was diminished in the Op-Control group indicating significant atrophy, but was partially preserved in both the MSC and MSC+Ex groups. Our results indicate that combining the beneficial effects of rat MSC and this exercise protocol was not sufficient to enhance behavioral recovery.
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The retrograde tracer cholera toxin beta-subunit (CTB) was used to trace long ascending propriospinal projections from neurons in the lumbosacral spinal cord to the upper cervical (C3) gray matter in adult male Sprague-Dawley rats. Following large 0.5 microl CTB injections restricted mainly to the upper cervical ventral horn (n=5), there were many lumbosacral CTB-positive neurons (14-17/section) in the intermediate gray and ventral horn (dorsal lamina VIII, medial VII extending into X) contralaterally, with fewer at corresponding ipsilateral locations. Labeled cells (4-8/section) were also observed in contralateral laminae IV-VI and the lateral spinal nucleus, with fewer ipsilaterally. ⋯ These results suggest direct projections from ventromedially located neurons of lumbar and sacral segments to the contralateral ventral gray matter of upper cervical segments, as well as from neurons in the intermediate but not superficial dorsal horn. They further suggest that some lumbosacral superficial dorsal horn neurons project to the upper cervical dorsal horn. These propriospinal projections may be involved in coordinating head and neck movements during locomotion or stimulus-evoked motor responses.
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Dihydropyrimidinase-like 3 (DPYSL3), a member of TUC (TOAD-64/Ulip/CRMP), is believed to play a role in neuronal differentiation, axonal outgrowth and possibly in neuronal regeneration. Recently, we have shown that in primary cortical neurons (PCN) NMDA and oxidative stress (H(2)O(2)) caused a calpain-dependent cleavage of DPYSL3 (62 kDa) resulting in the appearance of a lower molecular weight form (60 kDa) of DPYSL3. Our preliminary results had shown that antioxidants significantly reduced NMDA-induced DPYSL3 degradation, indicating involvement of ROS in calpain activation. ⋯ Neurochem. 95 (2), 466-474] and L-VGCC (nimodipine) inhibitors, H(2)O(2)-induced increase in [Ca(2+)](i), ROS generation and DPYSL3 truncation was blocked only by nimodipine. These results indicate that changes in Ca(2+) homeostasis resulting from ROS-dependent activation of L-VGCC are sufficient to induce probable calpain-mediated DPYSL3 truncation and demonstrate for the first time the role of ROS in the mechanism leading to glutamate-induced calpain activation and DPYSL3 protein degradation. The probable calpain-mediated DPYSL3 truncation may have significant impact on its interaction with actin and its assembly, and in turn on growth cone integrity.
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Hypoxic-ischemic injury in term neonates remains a significant cause of long-term neurological morbidity. The post-natal day 10 (P10) mouse is accepted as a model for the term human. This study was designed to assess the relationships between the duration of hypoxia-ischemia (HI) on P10 and the structural and functional neurological deficits that appear in the adult mouse as a consequence. ⋯ After correcting for motor deficits, there is evidence for persistence of "cued" learning but not spatial learning with increasing hypoxia-ischemia time on P10 in this model system.