Fumihiro Okumura

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The authors have previously reported that dynorphin A (1-17), an endogenous kappa opioid agonist, inhibits the current mediated through neuronal nicotinic acetylcholine receptors (nAChRs) without the involvement of opioid receptors or G-proteins. We have further characterized this action to elucidate the mechanisms. The nicotine-induced current was studied(More)
We have studied the effects of ketamine and pentobarbitone on acetylcholine (ACh) release from the rat frontal cortex using microdialysis. Ketamine 25, 50 and 100 mg kg-1 increased ACh release from the frontal cortex to 286%, 253% and 381% of basal release, respectively. In contrast, pentobarbitone 10, 20 and 40 mg kg-1 caused 73%, 78% and 96% inhibition of(More)
Using in vivo microdialysis, we have investigated the effects of propofol on acetylcholine (ACh) release from various regions of the rat brain. Propofol 25 and 50 mg kg-1 i.p. decreased basal ACh release from the frontal cortex by 70% and 85%, respectively. Propofol 25 and 50 mg kg-1 i.p. decreased basal ACh release from the hippocampus by 47% and 72%,(More)
  • J Wu, T Kikuchi, Y Wang, K Sato, F Okumura
  • 2000
Using microdialysis, we have examined the effects of ketamine on concentrations of total nitric oxide oxidation products (NOx-) in the rat hippocampus and striatum in vivo to investigate the relationship between anaesthesia and NOx- production in the brain. Ketamine 25, 50 and 100 mg kg-1 i.p. increased NOx- concentrations to mean 125 (SD 13)%, 165 (11)%(More)
BACKGROUND Alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA)-type glutamate receptors mediate fast excitatory synaptic transmission in the central nervous system. Although barbiturates have been shown to suppress the AMPA receptor-mediated responses, it is unclear whether this effect contributes to the anesthetic action of barbiturates. The(More)
Acetylcholine (ACh) release was measured by microdialysis. Addition of 10 nM L-DOPA to the perfusate significantly decreased ACh release, from the striatum of rats lesioned with 6-hydroxydopamine (6-OHDA), but not sham-operated rats. The L-DOPA-induced decrease was not affected by (-)-sulpiride which completely blocked D2- and D3-agonist-induced decrease in(More)
BACKGROUND PC12 cells, derived from rat pheochromocytoma, express neuronal nicotinic acetylcholine receptors (nAchRs) and P2X purinergic receptors, both of which resemble the receptors in postganglionic sympathetic neurons. The former is the established and the latter is the putative receptor to mediate fast synaptic transmission. The authors investigated(More)
In vitro muscle contracture responses in swine susceptible to malignant hyperpyrexia (MH) were similar to those found in muscle from humans susceptible to this anaesthetic complication, confirming the suitability of the pig as an animal model for studying MH. The results suggest that there are different degrees of susceptibility to MH. Whichever drug was(More)
Using microdialysis, we examined the effects of ketamine and pentobarbitone on acetylcholine (ACh) release from the rat hippocampus and striatum. Ketamine 25 and 50 mg kg-1 increased ACh release from the hippocampus to 295% and 353% of basal release, respectively, but not from the striatum. SCH 23390 1 mumol litre-1, a D1 antagonist, significantly inhibited(More)
Using striatal microdialysis, we studied effects of SKF 38393, a D1 agonist, and quinpirole, a D2 agonist, on the acetylcholine (ACh) release from the striatum of 6-hydroxydopamine (6-OHDA)-lesioned rats by local infusion into the striatum. The present experiments clearly demonstrated evidence for the existence of intrastriatal D1 and D2 receptors(More)