Brain research
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The purpose of the present study was to evaluate whether or not cardiovagal excitatory and sympatho-inhibitory pathways of the Bezold-Jarisch reflex at the NTS level were mediated by NMDA receptors. The Bezold-Jarisch reflex was activated by intravenous (i.v.) injection of serotonin in conscious rats before and after microinjection of phosphonovaleric acid (AP-5) a selective NMDA antagonist, into the NTS. ⋯ Methyl-atropine also blocked the bradycardic and hypotensive responses to Bezold-Jarisch reflex activation. The data show that in conscious rats the cardiovagal component of the Bezold-Jarisch reflex plays a major role in the cardiovascular changes produced by the activation of this reflex and suggest that the neurotransmission of the cardiovagal component of the Bezold-Jarisch reflex is mediated by NMDA receptors.
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Traumatic brain injury (TBI) causes impairments of both motor and spatial memory performances. Research is only beginning to reveal the biochemical mechanism(s) underlying these deficits. It has been postulated that reactive oxygen species such as the superoxide and hydroxyl radicals, as well as the peroxynitrite anion, are generated by injury and may play a critical role in the observed memory deficits. ⋯ Volumetric analysis of cortical tissue loss showed no significant differences between vehicle- and drug-injected animals. Similarly, histological examination of the hippocampus did not reveal any gross differences between the two groups. These results indicate that deferoxamine improves spatial memory performance, possibly through protection from neuronal dysfunction.
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The efficacy of ketamine (KET), a non-competitive NMDA receptor-channel blocker, was assessed in relieving nociceptive behaviors in neuropathic rats with tight ligations of the L5 and L6 spinal nerves. The antinociceptive effects of KET were dose- and time-dependent. A systemic injection of 0.01 mg/kg KET transiently (15-30 min) attenuated several nociceptive behaviors, including mechanical allodynia and hyperalgesia, cold allodynia, spontaneous pain, and cold stress-induced pain. ⋯ Systemic KET was most effective in decreasing the behavioral signs of mechanical allodynia and hyperalgesia, followed by cold allodynia, cold stress-induced pain, and spontaneous pain. The present results demonstrate that blockade of NMDA receptors effectively alleviates nociceptive behaviors in a rat model of peripheral neuropathy, substantiating the important role of these receptors in the central sensitization that underlies the maintenance of neuropathic pain. In addition, the ability of KET to reduce significantly a variety of nocifensive behaviors suggests that this clinically safe drug could be used in pain management for neuropathic patients.
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Noxious stimulation of dental nerves elicits marked changes in cardiovascular function. In order to investigate central pathways mediating reflex changes in cardiovascular activity, immunohistochemical localization of cells expressing the immediate-early gene, c-fos, was used to identify central nervous responding to noxious electrical stimulation of mandibular, incisor tooth dentin or chemical (capsaicin) stimulation of tooth pulp in the anesthetized rat. Injections of Fluoro-Gold were made in the lateral parabrachial region to identify efferent projections from the spinal trigeminal nucleus. ⋯ E. M.) subnuclei. The results demonstrate that nociceptive dental input received by the three subnuclei of the spinal trigeminal nucleus, particularly the subnucleus caudalis, is relayed to the lateral parabrachial nucleus.