Regulatory mechonisms for pxocytosis

(1)浦肯野细胞GABA能突触后电流的增强。从培养的大鼠浦肯野细胞中记录到自发抑制性突触后电流(IPSCs)和诱发的IPSCs。浦肯野细胞膜去极化后，这些GABA能IPSCs的大小增加。这种增加是由于突触后膜上GABA反应的增加，而不是突触前GABA释放的增加，并可能与细胞内钙浓度的增加和IP3诱导的钙释放而激活PLC有关。(2)大鼠听觉中继核内粘液型突触的时相传递在出生后发育。应用脑片全细胞膜片记录技术，对出生后4~13天(P4~P13)大鼠斜方体内侧核(MNTB)的突触传递进行了分析。在P4-P6动物中，诱发的EPSCs在幅度上波动很大，并以显著的异步性出现，其次是自发的EPSCs。随着动物的发育，诱发的EPSCs的幅度增大，上升时间变快。此外，突触传递变得锁相。EPSC波幅的变异系数(CV)随发育而降低(0.32±0.32)。[)P4-P5为0.03和0.05(SY+-)。[)P9-P11为0.01)。MEPSCs的波幅在所研究的出生后几天内没有变化(-30.2(SY+-)。[)0.3Pa，-70 mV)。CV值依赖于细胞外钙离子浓度([Ca~(2+)]_o)，并随细胞内[Ca~(2+)]_o浓度的升高而减小，这种[Ca~(2+)]_o依赖性随着发育向低[Ca~(2+)]_o方向转移。对突触前终末的直接斑片记录显示，在这些出生后的日子里，钙电流增加。该突触的锁相高保真传递可能是通过突触前终末递质释放机制中钙电流和钙敏感性的增加而实现的。

(1) Potentiation of GABAergic postsynaptic currents in the Purkinje cells. Spontaneous inhibitory postsynaptic currents (IPSCs) and evoked IPSCs were recorded from cultured Purkinje cells of the rat. Size of these GABAergic IPSCs were increased after membrane depolarization of Purkinje cells. The increase was due to the increased GABA response in the postsynaptic membrane rather than the increased release of GABA presynapitcally, and was likely coupled with the activation of PLC through the increased intracellular Ca concentration and the IP3 induced Ca release.(2) Postnatal development of phasic transmission in the clayx type synapse in the auditory relay nucleus of rat. Synaptic transmission in the medial nucleus of the trapezoid body (MNTB) of rats was analyzed in postnatal days of 4-13 (P4-P13) by applying the whole cell patch recording technique to brain slices. In P4-P6 animals, evoked EPSCs fluctuated extensively in amplitude and occurred in marked asynchrony, follwed by spontaneous EPSCs. With development of animals, the evoked EPSCs increased in amplitude, and the rise time became faster. In addition the synaptic transmission became phase-locked. The coefficient of variation (CV) of EPSC amplitude decreased with development (0.32(]SY.+-。[)0.03 for P4-P5 and 0.05(]SY.+-。[)0.01 for P9-P11). The amplitude of mEPSCs did not change throughout the postnatal days investigated (-30.2(]SY.+-。[)0.3 pA,at -70 mV). The CV was dependent on extracellular Ca2+ concentration ([Ca2+]o) and was reduced with the increase of [Ca2+]o, and this [Ca2+]o dependence was shifted towards lower [Ca2+]o with development. Direct patch recording of the presynaptic terminals demonstrated an increase in Ca2+ currents during these postnatal days. The phase-locked high-fidelity transmission in this synapse is achieved with development likely through the increase of Ca2+ currents and Ca2+ sensitivity of transmitter release mechanisms in the presynaptic terminal.