Neuroscience
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The phosphorylation of p38 mitogen-activated protein kinase (MAPK) in the dorsal root ganglion (DRG) promotes primary afferent sensitization. The role of p38MAPK signaling in the DRG in the pathogenesis of plantar incision hyperalgesia has not been investigated. ⋯ p38MAPK signaling in the DRG plays a crucial role in the development of primary afferent sensitization and pain behavior caused by plantar incision.
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Neonatal ventral hippocampus (NVH)-lesioned rats represent a neurodevelopmental impairment model of schizophrenia. Previous observations indicate that postpubertal NVH-lesioned rats exhibit impairments in prepulse inhibition (PPI), spontaneous locomotion and social interaction behavior. Here, we document the neurochemical basis of those defects. ⋯ Interestingly, phosphorylation of DARPP-32 (Thr 34) was decreased in the mPFC but increased in the striatum and CA1 region of NVH-lesioned rats compared to controls. Risperidone treatment restored increased DARPP-32 phosphorylation in the striatum and CA1 regions of NVH-lesioned rats but did not rescue CaMKII and PKCα autophosphorylation. Taken together, we find that impaired cognition observed in NVH-lesioned rats is associated with decreased CaMKII and PKCα activities in memory-related brain regions, changes not rescued by risperidone treatment.
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Long-term potentiation (LTP) can be induced by electrical stimulation and gives rise to an increase in synaptic strength at the first relay. This phenomenon has been associated with learning and memory and also could be the origin of several pathological states elicited by an initial strong painful stimulus, such as some forms of neuropathic pain. We used high-frequency electrical stimulation of the sciatic nerve in anesthetized rats to produce spinal LTP. ⋯ Furthermore, after 3h of LTP induction, PoT neurons could respond to cutaneous stimulation applied to different paws. Interestingly, the conduction velocities for the receptive field responses from the paw to the PoT cells were compatible with those of Aδ-fibers. Since PoT cells project to the insular cortex, the progressive increase in PoT activity and also the progressive unmasking of somatic receptive fields in response to LTP, place these cells in a key position to detect pain stimuli following central sensitization.
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Infection during early neonatal period has been shown to cause lasting neurological disabilities and is associated with the subsequent impairment in development of learning and memory ability and anxiety-related behavior in adults. We have previously reported that neonatal lipopolysaccharide (LPS) exposure resulted in cognitive deficits in juvenile rats (P21); thus, the goal of the present study was to determine whether neonatal LPS exposure has long-lasting effects in adult rats. ⋯ Neonatal LPS exposure also resulted in sustained inflammatory responses in the P71 rat hippocampus, as indicated by an increased number of activated microglia and elevation of interleukin-1β content in the rat hippocampus. This study reveals that neonatal LPS exposure causes persistent injuries to the hippocampus and results in long-lasting learning disabilities, and these effects are related to the chronic inflammation in the rat hippocampus.
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The ability to reweight visual and proprioceptive information is critical for maintaining postural stability in a dynamic environment. In this study, we examined whether visual anticipation of collision avoidance (AV) while standing could facilitate the down-weighting of altered proprioception in young and elderly adults. Twelve young (24.91±6.44years) and 12 elderly (74.8±6.42years) participants stood upright for 180s under two task conditions: (a) quiet stance (QS) and (b) standing while anticipating virtual objects to be avoided. ⋯ These results suggest that volitionally shifting reliance on vision when anticipating a collision AV event facilitates the down-weighting of altered proprioception. Elderly adults seem to be unable to dynamically exploit visual anticipation in order to down weight the altered proprioception possibly as a result of their more permanent up-weighting of the visual modality. Sensory reweighting seems to be a more time consuming process in aging which may have important clinical implications for falling.