Neuroscience
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Chronic musculoskeletal pain is one of the main symptoms found in Fibromyalgia with unclear etiology and limited pharmacological treatment. The aim of this study was to complex LIM in β-cyclodextrin (LIM-βCD) and then evaluate its antihyperalgesic effect in an animal model of chronic musculoskeletal pain. Differential scanning calorimetry and scanning electron microscopy was used for the characterization of the inclusion complex. ⋯ After intraplantar administration of capsaicin, LIM was able to significantly decrease time to lick. LIM-βCD has antihyperalgesic action superior to its uncomplexed form, with possible action in the dorsal horn of the spinal cord. These results suggest the possible applicability of LIM, uncomplexed or complexed with βCD, in conditions such as FM and neuropathic pain, for which there are currently only limited pharmacological options.
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The periodontal ligament (PDL) includes several types of nerve endings, such as Aβ-, Aδ-, and C-fibers, which play critical roles in detecting the strength and direction of occlusal force. Previous studies have demonstrated that electrical stimulation of the PDL activates the somatosensory and insular cortices. However, the profile of cortical excitation in response to mechanical PDL stimulation mostly remains unknown. ⋯ A paired-pulse protocol of mechanical stimulation revealed that the amplitude of the second response was smaller than the first response, in accordance with the shorter interstimulus interval. Systemic application of morphine, a potent blocker of nociception, reduced the amplitude of the maximum excitation, particularly in S2/IOR compared to S1. These results suggest that S1 and S2/IOR are principally excited by mechanical and electrical stimulation, respectively, and that S2/IOR is involved in nociception processing.
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Several brain structures including the brainstem, the cerebellum and the frontal cortico-basal ganglia network, with the primary and premotor areas have been shown to participate in the functional organization of gait initiation and postural control in humans, but their respective roles remain poorly understood. The aim of this study was to better understand the role of the supplementary motor area (SMA) and posterior cerebellum in the gait initiation process. Gait initiation parameters were recorded in 22 controls both before and after continuous theta burst transcranial stimulation (cTBS) of the SMA and cerebellum, and were compared to sham stimulation, using a randomized double-blind design study. ⋯ Functional inhibition of the SMA led to a shortened APA phase duration with advanced and increased muscle activity; during execution, it also advanced muscle co-activation and decreased the duration of stance soleus activity. Cerebellar functional inhibition did not influence the APA phase duration and amplitude but increased muscle co-activation, it decreased execution duration and showed a trend to increase velocity, with increased swing soleus muscle duration and activity. The results suggest that the SMA contributes to both the timing and amplitude of the APAs with no influence on step execution and the posterior cerebellum in the coupling between the APAs and execution phases and leg muscle activity pattern during gait initiation.
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Few researchers have investigated the direction of commissural axon projections on the contralateral side of the vertebrate embryonic spinal cord, especially for comparison between its different regions. In this study, pCAGGS-GFP plasmid expression was limited to different regions of the chicken embryonic spinal cord (cervical, anterior limb, anterior thorax, posterior thorax and posterior limb) at E3 using in ovo electroporation with modified electrodes and optimal electroporation conditions. Then open-book technique was performed at E6 to analyze the direction of axon projections in different spinal cord regions. ⋯ The ratio of rostral and caudal projections was significantly different between the five investigated regions (P<0.05), except between the cervical region and the anterior limb (P>0.05). The projections were most likely to be rostral for the posterior limb followed by the posterior thorax, cervical region, anterior limb and anterior thorax. Our data for the direction of the commissural axon projections will be helpful in the future analyses of axon projection mechanisms and spinal cord-brain circuit formation.
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The insular cortex is a critical brain region involved in nicotine addiction. However, its specific cellular and synaptic mechanisms underlying nicotine addiction remains largely unknown. In the present study, we examined how nicotine modulates synaptic transmission and plasticity in layer V pyramidal neurons of the mouse insular cortex. ⋯ Blockade of GABAA receptors or β2-containing nAChRs prevented the effects of nicotine on synaptic potentiation. Taken together, these results suggest that in layer V pyramidal neurons of the insular cortex, activation of β2-containing nAChRs expressed in non-FS interneurons suppresses synaptic potentiation through enhancing GABAergic synaptic transmission. These findings provide important insights into the cellular and synaptic mechanisms of insular cortical changes in nicotine addiction.