Anesthesiology
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Ketamine was previously suggested to relax vascular smooth muscle by reducing the intracellular Ca2+ concentration ([Ca2+]i). However, no direct evidence is available to indicate that ketamine reduces the [Ca2+]i in vascular smooth muscle of systemic resistance arteries. ⋯ The action of ketamine on contractile response to norepinephrine consists of endothelium-dependent vasoconstricting and endothelium-independent vasodilating components. The direct vasorelaxation is largely a result of reduction of[Ca2+]i in vascular smooth muscle cells. The [Ca2+]i-reducing effects are caused by inhibitions of both voltage-gated Ca2+ influx and norepinephrine-induced Ca2+ release from the intracellular stores.
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Halothane is extensively (approximately 50%) metabolized in humans and undergoes both oxidative and reductive cytochrome P450-catalyzed hepatic biotransformation. Halothane is reduced under low oxygen tensions by CYP2A6 and CYP3A4 in human liver microsome to an unstable free radical, and then to the volatile metabolites chlorodifluoroethene (CDE) and chlorotrifluoroethane (CTE). The free radical is also thought to initiate lipid peroxidation. Halothane-dependent lipid peroxidation has been shown in animals in vitro and in vivo but has not been evaluated in humans. This investigation tested the hypothesis that halothane causes lipid peroxidation in human liver microsomes, identified P450 isoforms responsible for halothane-dependent lipid peroxidation, and tested the hypothesis that lipid peroxidation is prevented by inhibiting halothane reduction. ⋯ Halothane causes lipid peroxidation in human liver microsomes, which is catalyzed by CYP2A6, and inhibition of halothane reduction prevents halothane-dependent lipid peroxidation in vitro.
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Inflammatory pain can be effectively controlled by an interaction of opioid receptors on peripheral sensory nerve terminals with opioid peptides released from immune cells upon stressful stimulation. To define the source of opioid peptide production, we sought to identify and quantify populations of opioid-containing cells during the course of Freund's complete adjuvant-induced hind paw inflammation in the rat. In parallel, we examined the development of stress-induced local analgesia in the paw. ⋯ The degree of endogenous pain inhibition is proportional to the number of opioid peptide-producing cells, and distinct leukocyte lineages contribute to this function at different stages of inflammation. These mechanisms may be important for understanding pain in immunosuppressed states such as cancer, diabetes, or AIDS and for the design of novel therapeutic strategies in inflammatory diseases.
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Newborn neuromuscular junctions are more sensitive to d-tubocurarine than more mature preparations. It is unclear whether the same modifications occur with newer nondepolarizing agents and depolarizing agent succinylcholine. The purpose of this study was to determine the relative sensitivity of newborn neuromuscular junctions to succinylcholine and five nondepolarizing agents. ⋯ The newborn neuromuscular junction of the rat shows an increased sensitivity to all neuromuscular blocking agents tested, including succinylcholine. However, the potency ratio was greater for nondepolarizing than depolarizing drugs. The optimal dose of these agents for certain situations such as cesarean section and anesthesia in neonates should be reassessed.