Effect of activation of mitochondrial ATP sensitive potassium channel and calcium activated potassium channel on the permeability transition of mitochondria from both normal and ischemic rat brain / 中国应用生理学杂志

<p><b>AIM</b>To clarify whether the activation of mitochondrial ATP sensitive potassium channel and calcium activated potassium channel can influence the permeability transition of normal and ischemic brain mitochondria.</p><p><b>METHODS</b>spectrophotometry was used to determine the effect of the two mitochondrial potassium channel agonists on the swelling of normal and ischemic brain mitochondria respectively.</p><p><b>RESULTS</b>In normal mitochondria, diazoxide and NS1619 could inhibit the decrease of calcium induced mitochondrial absorbance at 520 nm (A520), which were blocked by atractyloside. When compared with the normal mitochondria, mitochondrial A520 decrease in ischemic brain was even more rapid. Diazoxide and NS1619 could still inhibit the calcium induced mitochondrial A520 decrease, which were blocked by atractyloside.</p><p><b>CONCLUSION</b>Activation of mitochondrial ATP sensitive potassium channel and calcium activated potassium channel can protect brain mitochondria in vitro probably via influencing the mitochondrial permeability transition.</p>

Changes in field excitatory postsynaptic potential and population spike in CA1 region of rat hippocampal slices following low-frequency stimulation / 生理学报

The technique of extracellular recording was used and the changes in the slope of field excitatory postsynaptic potential (S-EPSP) and the amplitude of population spike (A-PS) were observed when homosynaptic long-term depression (LTD) was induced by low-frequency stimulation (LFS) in the CA1 region of rat hippocampal slices. After LFS of 900 pulses at 1 Hz was delivered, S-EPSP and A-PS were reduced by 35.4 +/- 5.3% and 68.0 +/- 7.2%, respectively. When LFS of 450 pulses at 1 Hz was delivered, S-EPSP and A-PS were reduced by 14.3 +/- 2.3% and 36.8 +/- 6.7%, respectively. In both groups, the change in A-PS was significantly greater than that in S-EPSP (P<0.01). The changes in both indexes in the group of 900 pulses were greater than those in the group of 450 pulses (P<0.05). High Mg(2+) (4 mmol/L) could attenuate the synaptic transmission, but did not affect the induction of LTD. In the high Mg(2+) medium, the change in A-PS induced by LFS was also markedly greater than that in S-EPSP (P<0.01). These results indicate that the level of homosynaptic LTD induced by LFS is dependent not only on the numbers of pulses of LFS delivered, but also on the selection of evaluating index.

Studies on properties of depotentiation of long-term potentiation induced by low frequency stimulation in CA1 neurons of rat hippocampal slices / 中国应用生理学杂志

<p><b>AIM AND METHODS</b>The parameters of low frequency stimulation (LFS) were altered systematically (frequencies of 1, 3 or 5 Hz; number of pulses of pulses of 300 or 900; and time lag after high frequency stimulation (HFS) of 20 or 100 min) and examined their effects on depotentiation (DP) of long-term potentiation (LTP) of synaptic transmission in CA1 neurons in hippocampal slices of rat.</p><p><b>RESULTS</b>LTP could be induced by HFS (two trains of 100 Hz, 100 pulses, separated by 30 s) and be reversed to produce DP by a train of LFS of 900 pulses at 3 Hz given 20 min after HFS. DP induced by LFS could be blocked by NMDA receptor antagonist AP5 (50 micromol/L). And significantly reduced effect was observed for LFS at 1 Hz or 5 Hz, with smaller numbers of pulses or a longer time lag from LFS to HFS.</p><p><b>CONCLUSION</b>The above results indicate that DP induced in CA1 neurons of rat hippocampal slices is strongly dependent on the parameters of LFS, and the process may be mediated through the NMDA receptor.</p>