Developmental changes in synaptic and extrasynaptic N-methyl-D-aspartate receptors in cultured rat hippocampal neurons / 南方医科大学学报

<p><b>OBJECTIVE</b>To investigate changes in synaptic and extrasynaptic N-methyl-D-aspartate receptors (NMDAR) during the development of cultured rat hippocampal neurons.</p><p><b>METHODS</b>Synaptic and extrasynaptic NMDAR channel currents were recorded from 1-day-old rat hippocampal neurons cultured for 1 and 2 weeks with patch-clamp technique in whole-cell configuration and outside-out configuration, respectively.</p><p><b>RESULTS</b>The amplitude of NMDAR-mediated miniature excited postsynaptic current (Meps(CNMDA)) decreased in neurons cultured for 2 weeks as compared with that recorded in neurons cultured for 1 week, and the 2-week neurons showed also much lowered sensitivity to selective NR2B blocker ifenprodil. The amplitude and open probability of extrasynaptic NMDAR in the 2-week neurons were significantly higher than those in the 1-week neurons, but the neurons differred little in conduction and reverse potential. Ifenprodil decreased the high conductance and open probability in both neurons, but the effect was more potent in the 2-week ones.</p><p><b>CONCLUSIONS</b>There can be developmental changes in synaptic and extrasynaptic NMDAR channel currents in cultured rat hippocampal neurons, indicating that different NMDAR subtypes are expressed in the synaptic and extrasynaptic regions during the development of the hippocampal neurons. In 1-week neurons, NR2B are predominant both in synaptic and extrasynaptic regions, and at 2 weeks, synaptic NR2B are replaced by NR2A but NR2B still remains the predominant subtypes outside the synapses.</p>

Neuroprotection of chloride channel blockers against NMDA-induced apoptosis of cultured rat hippocampal neurons / 南方医科大学学报

Activation of N-methyl-d-aspartic acid (NMDA) receptor plays an important role in neuronal apoptosis induced by cerebral ischemia but the underlying mechanisms are still unclear. The present study examined the neuroprotection of three chloride blockers in an in vitro cell model of cerebral ischemia established by treatment of cultured rat hippocampal neurons with NMDA. Hoechst 33258 staining and MTT assay were used to detect neuronal apoptosis and cell viability, respectively. The neuroprotective effects of chloride channel blockers on the cell viability and neuronal apoptosis were only observed when the blockers were applied before NMDA exposure. In comparison with DIDS, SITS showed more potent protective effect in a dose-dependent manner, whereas NPPB showed no significant neuroprotective effect. The results demonstrate that pretreatment with both SITS and DIDS have protective effect against neuronal apoptosis, which is achieved by blocking both NMDA receptor and chloride channel.