Neuroscience
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Randomized Controlled Trial Comparative Study
What does autonomic arousal tell us about locomotor learning?
Walking onto a stationary sled previously experienced as moving induces locomotor aftereffects (LAE, or "broken escalator phenomenon"). This particular form of aftereffect can develop after a single adaptation trial and occurs despite subjects being fully aware that the sled will not move. Here, we investigate whether such strong LAE expression may relate to arousal or fear related to instability during the gait adaptation process. ⋯ Hence, gait velocity and trunk sway components of the LAE are differentially related to kinematic and autonomic parameters during the early and late adaptation phase. The finding that EDA is a predictor of LAE expression indicates that autonomic arousal or fear-based mechanisms can promote locomotor learning. This could in turn explain some unusual characteristics of this LAE, namely its resistance to explicit knowledge and its generation with just a single adaptation trial.
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Randomized Controlled Trial
Abnormal expression of voltage-gated sodium channels Nav1.7, Nav1.3 and Nav1.8 in trigeminal neuralgia.
Voltage-gated sodium channels have been implicated in acute and chronic neuropathic pain. Among subtypes, Nav1.7 single mutations can cause congenital indifference to pain or chronic neuropathic pain syndromes, including paroxysmal ones. This channel is co-expressed with Nav1.8, which sustains the initial action potential; Nav1.3 is an embrionary channel which is expressed in neurons after injury, as in neuropathic conditions. ⋯ We found that Nav1.7 was downregulated in TN (P=0.017) and Nav1.3 was upregulated in these patients (P=0.043). We propose a physiopathological mechanism for these findings. Besides vascular compression of TN, this disease might be also a channelopathy.
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Randomized Controlled Trial Clinical Trial
Enhancement of morphine analgesia by the alpha 2-adrenergic antagonist yohimbine.
Although interactions between opioids and adrenergic agonists in the treatment of pain have been demonstrated in humans, the contribution of specific adrenergic receptors in this interaction remains to be clarified. In a double-blind, placebo-controlled study in male patients with postoperative dental pain, we investigated the effect of preoperative administration of the alpha 2-adrenergic antagonist, yohimbine, on analgesia produced by postoperative intravenous morphine. Although yohimbine by itself did not affect the pain, the overall analgesic effect of morphine was significantly enhanced in the presence of yohimbine. This report is the first to demonstrate that an alpha 2-adrenergic antagonist enhances opiate analgesia in humans.