| Budget Amount *help |
¥3,100,000 (Direct Cost: ¥3,100,000)
Fiscal Year 1998: ¥1,000,000 (Direct Cost: ¥1,000,000)
Fiscal Year 1997: ¥2,100,000 (Direct Cost: ¥2,100,000)
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| Research Abstract |
Background : Our recent studies demonstrated that posttraining exposure to enflurane enhanced memory consolidation both in the active avoidance learning and in the radial maze learning of mice (Komatsu, et al., 1993,1998). Long-term potentiation (LTP) is a long-lasting increase in synaptic efficacy induced by a brief stimulus train, and is thought to underlie some forms of neural plasticity such as learning and memory (Oda, et al., 1998). In the present study, we examined the effects of enflurane on the LTP in the hippocampus.
Methods : Extracellular recordings of field excitatory post synaptic potentials (EPSPs) were performed with amicroelectrode positioned in CA1 area of the hippocampal slices obtained from 2 to 3 weeks-old rats or mice. The slices were submerged beneath a continuously superfusing (at a flow rate of 1 ml/min) solution saturated with 95% OィイD22ィエD2 and 5% COィイD22ィエD2. The field EPSPs evoked by test stimulus applied to the Schaffer collateral/commissural pathway (Sch/c
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om) were monitored to assess whether enflurane affects the induction or expression of LTP. Enflurane vaporized at 2 and 5 vol % was ewuilibrated in the superfusing solution. The enflurane-contained solution was applied for 20 minutes after establishment of LTP, more than 15 mm after tetanic stimulation through a standard vaporizer (2 and 5 vol. %) was equilibrated in the and bath applied to the slice at a constant flow of 1 ml/min.
Results : The tetanization induced LTP in the initial slope and amplitude of the field EPSPs in the control solution. When enflurane was added to the superfusing solution, over concentration range of 2.0 to 5.0 vol. %, after establishment of LTP, the EPSPs were diminished and usually (9 out of 16) recovered to the preanesthetic level after washout procedure. But, in some slices (7 out of 16), after washout of enflurane, the slope and amplitude of EPSPs exhibited significant increase (> 20%) beyond the preanesthetic level.
Conclusions : These results suggest that tentative application of enflurane to the hippocampus can enhance the LTP of Sch/com evoked EPSP at CA1 area. Thus facilitation of memory consolidation by posttraining exposure to enflurane might be mediated ,at least in part, by apostanesthetic enhancement of LTP induction/expression in the hippocampus CA1 area. Less
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