Brain research
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Aside from anatomical repairs, the reestablishment of sensory and motor innervations for proper functional recovery is one of the fundamental objectives of reconstructive surgery. The heterotopic transfer of autologous tissues is likely to result in a size discrepancy between the donor and recipient nerves, which will have a negative influence on regeneration. Twenty Wistar albino female rats were used in a study that was divided into two main groups: tibial-peroneal (TP) and peroneal-tibial repair (PT). ⋯ In both TP and PT groups, the increase in the axon number, axon area and myelin thickness were statistically different in favor of the vein graft sides. An appearance of vacuoles and degenerated pertinacious material within the myelin sheath of EtoE sides was seen. A histomorphological examination of the sections proximal to, from, and distal to the repair zone over three months revealed less epineural scarring, a thinner epineurium, more regenerated axons and fewer inflammatory cells in groups where vein grafting was used, because the vein graft provided additional mechanical and chemical support in the size discrepancy of the nerve regeneration.
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Behavioral investigations have shown that general anesthetics at low concentration have enhancing effects on learning and memory in some animal models. In the present experiments, in order to elucidate the cellular mechanisms underlying such memory enhancement, the effects of anesthetics at low doses on synaptic plasticity in the hippocampus were investigated. Tight-seal whole-cell recordings were made from CA1 pyramidal cells in hippocampal slices prepared from adult male mice, and the effects of subanesthetic concentrations of the volatile anesthetic sevoflurane on the glutamatergic excitatory postsynaptic currents (EPSCs) were investigated. ⋯ These observations suggest that sevoflurane at anesthetic concentration presynaptically inhibits excitatory synaptic transmission and at subanesthetic concentration postsynaptically enhances excitatory synaptic transmission in the hippocampal CA1 region. Further, subanesthetic sevoflurane seems to exert facilitatory effects on the EPSP-to-spike coupling process in the postsynaptic neurons. These results might provide clues as to the cellular mechanism of light level of sevoflurane anesthesia.
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Our recent event-related brain potential (ERP) study disentangled the neural mechanisms of empathy for pain into an early automatic emotional sharing component and a late controlled cognitive evaluation process. The current study further investigated gender difference in the neural mechanisms underlying empathy for pain by comparing ERPs associated with empathic responses between male and female adults. ⋯ However, females were different from males in that the long-latency empathic response showed stronger modulation by task demands and that the ERP amplitudes at 140-180 ms were correlated with subjective reports of the degree of perceived pain of others and of unpleasantness of the self. Our ERP results provide neuroscience evidence for differences in both the early and late components of empathic process between the two sexes.
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The use of topical non-steroidal anti-inflammatory drugs, such as diclofenac, for the treatment of temporomandibular disorders-related myofascial pain is based on the premise that their analgesic effect is mediated by a local action on the excitability of muscle nociceptors, despite a lack of muscle inflammation in these patients. To investigate if diclofenac has an effect on muscle afferent fibers in the absence of inflammation, in vivo recordings of the response of masseter muscle afferent fibers to mechanical and noxious chemical (hypertonic saline) stimulation were made in anesthetized Sprague-Dawley rats. It was observed that injection of diclofenac (0.1 or 1 mg/ml) alone could elevate afferent mechanical threshold for a 10 min period post-injection. ⋯ Additional experiments were undertaken to investigate whether activation of ATP-sensitive potassium (K ATP) channels could contribute to the effects of diclofenac. The K ATP channel opener pinacidil (0.1 mg/ml) significantly enhanced potassium chloride-evoked afferent discharge consistent with the concept that masseter afferent fibers have functional K ATP channels, however, subsequent experiments indicated that diclofenac (1 mg/ml) significantly suppressed potassium chloride-evoked afferent discharge and that pinacidil did not affect hypertonic saline-evoked afferent discharge. These results indicate that diclofenac can exert a "local anesthetic-like" action on masseter afferent fibers in the absence of inflammation, but that this effect does not appear to involve the opening of K ATP channels.
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The basolateral amygdala (BLA) is known to be involved in emotional and stress responses, while the dentate gyrus (DG), a subfield of the hippocampus, is implicated in learning and memory. Together, the BLA-DG neuronal pathway is thought to link memory with emotional and physiological stress responses. To assess whether neonatal isolation, a known early life stressor, has enduring effects on bidirectional neuroplasticity in adulthood, changes in long-term potentiation (LTP) and long-term depression (LTD) of BLA-DG synapses were recorded in neonatally isolated and non-handled freely behaving adult male rats. ⋯ Following a 1-week postsurgical recovery period, either LTP (100-pulse, 5-Hz theta-burst stimulation [TBS]) or LTD (900-pulse, 1-Hz low-frequency stimulation [LFS]) was induced in the DG of both groups. ISO rats showed significantly enhanced levels of both LTP and LTD compared to NH counterparts. These results indicate that neonatal isolation stress alters bidirectional neural plasticity in BLA-DG synapses, which may help to clarify the development of neural mechanisms linking emotional and stress responses in the amygdala with memory consolidation and information processing in the hippocampus.