Buyang Huanwu Decoction (BYHWD), a traditional Chinese medicine, has been developed as a drug to be used for treatment of stroke for hundreds of years. However, the underlying mechanisms remain unknown. In the present study, the effects of BYHWD on delayed neuronal death of hippocampus after transient forebrain ischemia were examined in rats. Transient forebrain ischemia in a duration of 15 rain was induced with the four-vessel occlusion method. BYHWD (per 6.65g/kg) was given orally to rats twice each day for 7 days before ischemia. In BYHWD-pretreated rats, the neuronal injury in the hippocampal CA1 region was significantly less than that of controls. Oral administration of BYHWD also markedly attenuated the number of TUNEL-positive neurons and suppressed the expression of caspase-3p20, a product of catalytically active caspase-3, in the CA1 region. Our results suggest that an inhibition of caspase-3 and apoptosis by BYHWD may oartially account for its neuroorotection against ischemic iniury in the hippocampal CA1 region.

Evoked postsynaptic potentials of CA1 pyramidal neurons in rat hippocampus were studied during 48h after severe ischemic insult using in vivo intracellular recording and staining techniques. Postischemic CAI neurons displayed one of three distinct response patterns following contralateral commissural stimulation. At early recirculation times (0-12h) approximately 50% of neurons exhibited, in addition to the initial excitatory postsynaptic potential, alate depolarizing postsynaptic potential lasting for more than 100ms. Application of dizocilpine maleate reduced the amplitude of late depolarizing postsynaptic potential by 60% Other CAI neurons recorded in this interval failed to develop late depolarizing postsynaptic potentials but showed a modest blunting of initial excitatory postsynaptic potentials (non-late depolarizing postsynaptic potential neuron). The proportion of recorded neurons with late depolarizing postsynaptic potential characteristics increased to more than 70% during 13-24h after reperfusion. Beyond 24h reperfusion, 20% of CA1 neurons exhibited very small excitatory postsynaptic potentials even with maximal stimulus intensity. The slope of the initial excitatory postsynaptic potentials in late depolarizing postsynaptic potential neurons increased to 150% of control values up to 12h after reperfusion indicating a prolonged enhancement of synaptic transmission. In contrast, the slope of the initial excitatory postsynaptic potentials in non-late depolarizing postsynaptic potential neurons decreased to less than 50% of preischemic values up to 24h after reperfusion indicating a prolonged depression of synaptic transmission. More late depolarizing postsynaptic potential neurons were located in the medial portion of CA1 zone where neurons are more vulnerable to ischemia whereas more non-late depolarizing postsynaptic potential neurons were located in the lateral portion of CA1 zone where neurons are more resistant to ischemia. The result from the present study suggests that late depolarizing postsynaptic potential and small excitatory postsynaptic potential neurons may be irreversibly injured while non-late depolarizing postsynaptic potential neurons may be those that survive the ischemic insult. Alterations of synaptic transmission may be associated with the pathogenesis of postischemic neuronal injury.

Pyramidal neurons in the CAI field of the hippocampus die a few days after transient cerebral ischemia.4,21 Excessive excitatory synaptic activation following reperfusion is thought to be responsible for such de-layed cell death. 4,24 However, it remains controversial whether excitatory synaptic transmission in the CAI field is increased following reperfusion.2'3'1'1u18'26 Here we report a novel postsynaptic potential evoked from CAI pyramidal neurons preceding cell death after transient forebrain ischemia with intracellular record-ing and staining techniques in vivo. This result indicates the dramatic alteration of synaptic transmission in CAI neurons after transient ischemia. The ischemia-induced postsynaptic potential may be associated with the postischemic neuronal injury. Copyright

It has been shown that intracellular Ca2+ in hippocampal CA1 neurons is elevated during ischemia and at early period following reperfusion. This Ca2+ overload has been suggested to be involved in ischemic brain damage. In normal CAI neurons, the major mechanism allowing Ca2+ entry from the extracellular compartment is the opening of voltage-gated Ca2+ channels. The aim of the present study was to explore whether L-type calcium channel in hippocampal CA1 neurons changed at early period of reperfusion after ischemia. Transient forebrain ischemia in a duration of 15 min was induced by the use of the 4-vessel occlusion method in rats. Single L-type calcium currents were recorded in cell-attached patches of actually dissociated hippocampal CAI neurons. After ischemia, average total patch current of L-type Ca2+ channels significantly increased in CAI neurons when compared with that of control. This ischemia-induced enhancement in channel function was due to a higher channel open probability. Further analysis of single channel kinetics showed a prolonged open time and an increased opening frequency in postischemic channels. It is suggested that the functional enhancement in L-type calcium channels may partially account for the postischemic increase in intracellular Ca2+ concentration of CA1 neurons following ischemia.

采用膜片钳内面向外式技术，在急性分离成年大鼠海马CAl区锥体细胞上记录到了外向整流氯离子通道（outwadly rectifving chloride channel, ORCC），长时间去极化（I>60mv）刺激后，在30%的游离膜片上记录到有外向整流特性的单通道氯电流，膜电位在-60mV到0mV之间的单通道电导为（16.58±1.54）Ps(n=10），而在0mv到+60mv之间电导为（40.92±3.17）pS，通道开放概率有明显的电压依赖性（膜电位-60mV时，P=0.44±0.12；膜电位为+60mv时，Pa=0.86±0.06，n=10），在对称C1-浓度（150 retool/L）时，通道翻转电位为（-4.17±1.84）mv。当溶液中部分NaCl被葡萄糖酸钠替代后，翻转电位为：（-34.23±4.86）mV（C1-1/[C1一]。-（30mmol/L）/（150 mmol/L）），接近氯离子通道的理论值，这表明通道具有氯离子选择性，浴槽液中分别加入氯通道阻断剂DIDS和SITS可以使+40mV的通道开放概率从（0.83±0.06）和（0.86±0.06）分别降低到（0.12±0.05）和（0.13±0.04）n=5)，冲洗后可使开放概率基本恢复，上述研究结果显示，在成年大鼠海马CAl神经元上存在外向整流氯离子通道。