Anesthesiology
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To learn more about pain mechanisms produced by surgery, responses of wide dynamic range (WDR) and high threshold (HT) dorsal horn neurons were studied before and after an incision. For this study, an incision was made in a mechanically insensitive area of the receptive field (RF) of the dorsal horn neuron in the plantar aspect of the foot and changes in mechanical response properties were studied. ⋯ These results suggest that incisions in mechanically insensitive areas of the RF of dorsal horn neurons produced little change in background activity; expansion of pinch RFs outside the injury was common. Changing a mechanically insensitive area of the RF of WDR neurons to a mechanically sensitive area by an incision could contribute to pain behaviors that indicate primary mechanical hyperalgesia in behavioral studies.
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The local anesthetic bupivacaine exists in two stereoisomeric forms, R(+)- and S(-)-bupivacaine. Because of its lower cardiac and central nervous system toxicity, attempts were made recently to introduce S(-)-bupivacaine into clinical anesthesia. We investigated stereoselective actions of R(+)-and S(-)-bupivacaine toward two local anesthetic-sensitive ion channels in peripheral nerve, the Na+ and the flicker K+ channel. ⋯ Bupivacaine block of Na+ channels shows no salient stereoselectivity. Block of flicker K+ channels has the highest stereoselectivity ratio of bupivacaine action known so far. This stereoselectivity derives predominantly from a difference in k(-1), suggesting a tight fit between R(+)-bupivacaine and the binding site. The flicker K+ channel may play an important role in yet unknown toxic mechanisms of R(+)-bupivacaine.
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The hypermetabolic state induced by acute endotoxemia and malignant hyperthermia (MH) may be indistinguishable. The aims of this study were (1) to investigate the differences between MH and sepsis, (2) to determine whether acute endotoxemia can trigger MH, and (3) to establish the effects of dantrolene in these two disorders. ⋯ Endotoxemia does not trigger MH, but may worsen outcome if it occurs.