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.

Gao, T. M., E. M. Howard, and Z. C. Xu. Transient neurophysio-logical changes in CA3 neurons and dentate granule ceils after severe forebrain ischemia in vivo. J. Neurophysiol. 80: 2860-2869, 1998. The spontaneous activities, evoked synaptic responses, and membrane properties of CA3 pyramidal neurons and dentate granule cells in rat hippocampus were compared before ischemia and s7 days after reperfusion with intracellular recording and staining techniques in vivo. A four-vessel occlusion method was used to induce ～14 min of ischemic depolarization. No significant change in spontaneous firing rate was observed in both cell types after reperfusion. The amplitude and slope of excitatory postsynap-tic potentials (EPSPs) in CA3 neurons decreased to 50% of control values during the first 12h reperfusion and returned to preischemic levels 24h after reperfusion. The amplitude and slope of EPSPs in granule cells slightly decreased 24-36 h after reperfusion. The amplitude of inhibitory postsynaptic potentials in CA3 neurons transiently increased 24h after reperfusion, whereas that in granule cells showed a transient decrease 24-36 h after reperfusion. The duration of spike width of CA3 and granule cells became longer than that of control values during the first 12h reperfusion. The spike threshold of both cell types significantly increased 24-36h after reperfusion, whereas the frequency of repetitive firing evoked by depolarizing current pulse was decreased during this period. No significant change in rheobase and input resistance was observed in CA3 neurons. A transient increase in rheobase and a transient decrease in input resistance were detected in granule cells 24 36h after reperfusion. The amplitude of fast afterhyperpolarization in both cell types increased for 2 days after ischemia and returned to normal values 7 days after reperfusion. The results from this study indicate that the neuronal excitability and synaptic transmission in CA3 and granule cells are transiently suppressed after severe forebrain ischemia. The depression of synaptic transmission and neuronal excitability may provide protection for neurons after isch-emic insult.

Neurophysiological changes of hippocampal neurons were compared before and after transient forebrain ischemia using intracellu-lar recording and staining techniques in vivo. Ischemic depolarization (ID) was used as an indication of severe ischemia. Under halo-thane anesthesia, approximately 13 rain of ID consistently produced severe neuronal dam-age in the CA1 region of rat hippocampus, while CA3 pyramidal neurons and dentate granule cells remained intact. After such se-vere ischemia, approximately 60% of the CA1 neurons exhibited a synaptic potentia-tion. The excitability of these neurons pro-gressively decreased following reperfusion. Approximately 30% of the CA1 neurons showed a synaptic depression following ischemia. The excitability of these neurons transiently decreased following reperfusion. After ischemia of the same severity, both synaptic transmission and excitability of CA3 and granule cells transiently depressed. These data suggest that ischemia-induced synaptic potentiation may be associated with the pathogenesis of neuronal damage fol-lowing ischemia, and that the synaptic de-pression may have protective effects on hip-pocampal neurons after ischemic insult.

Using inside-out configuration of patch clamp techniques, ATP modulation of BKca channels was studied in hippocampal CAI pyramidal neurons of adult rat. Intracellular ATP application markedly increased BKca channel activity, and this ATP-produced increase in BK, channel activity was characterized by a higher opening frequency with no changes in channel open times. In the presence of specific inhibitor against protein kinase A, H-89, ATP did not induce any increase in the channel activity. Furthermore, adding H-89 after addition of ATP reversed the modulation produced by ATE In contrast, protein kinase C inhibitor chelerythrine exerted no apparent effects on ATP-induced channel activation. The present study suggests that BKca channels from hippocampal CA1 pyramidal neurons could be modulated by ATP via a functionally associated orotein kinase A-like orotein.