| Budget Amount *help |
¥1,700,000 (Direct Cost: ¥1,700,000)
Fiscal Year 1988: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1987: ¥1,200,000 (Direct Cost: ¥1,200,000)
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| Research Abstract |
Long-term potentiation (LTP) of synaptic transmission was intracellularly studied in slice preparation obtained from kittens aged 30-40 days after birth. Test stimulation of white matter (0.1 Hz) evoked in layer II-III cells a fast excitatory postsynaptic potential (fEPSP) and a slow EPSP (sEPSP). Conditioning stumulation of white matter (2 Hz, 15 minutes) produced LTPs of f- (8 cells out of 13 tested cells) and sEPSP (10/13). The maximum rate of rise of fEPSP was increased 1.6 times and the amplitude of sEPSP 3 times. The LTPs occurred together in 7 cells and separately in 4 cells (1 for fEPSP and 3 for sEPSP), suggesting that the LTP in f- and sEPSP occurs independently. The LTP raraly occurred in mature animals (120-150 days).
fEPSP and sEPSP were mediated by non-NMDA and NMDA receptors, respectively. 2-amino-5-phosphonovalerate (APV), a specific NMDA antagonist, abolished the sEPSP, while it did not affect fEPSP. Kynurenate, a glutamate blocker for both NMDA and non-NMDA types, depressed the fEPSP. Therefore, conditioning stimulation of white matter seems to produce LTPs in both non-NMDA mediated and NMDA-mediated transmission.
The involvement of NMDA receptors in induction of LTP in fEPSP was studied in cells perfused with solution containing 100 uM APV, which was sufficient to block NMDA receptors. The LTP of fEPSP occurred just the same way as in control solution. No significant difference was found in the frequency (7/11 in APV, 8/13 in control), the magnitude of LTP (1.5+0.2, 1.6+0.4) or its time course. Therefore, it is concluded the activation of NMDA receptors is not prerequisite for induction of LTP in kitten visual cortex. This conclusion was confirmed by examining the LTP of field potentials recorded in layer II-III.
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