Studies on functional properties of the inhibitory neurons in the hippocampus of the rat using slice-patch techniques and newly modified pr ocedur es.

在大鼠海马齿状回切片中，纳马斯基显微镜下发现了主要神经元（颗粒细胞）和局部抑制性神经元（篮状细胞）。采用全细胞膜片钳技术和快速灌注（y管）法研究5-羟色胺（5-HT）对这些神经元的影响。在颗粒细胞中，外用5-HT （0.2-100 uM）没有引起任何电流，但在篮状细胞中，以-63mV的保持电位诱导了明确的内向电流。5-HT响应的I-V关系显示，在0mV左右有反转电位，在-60mV以下电位处有负斜率电导。为了比较这些5-HT受体的功能特性，我们研究了小鼠骨髓巨核细胞中新发现的ADP（腺苷-5'-二磷酸）受体。当Cs +作为主要内部阳离子阻断k -电流时，将ADP （10-100 uM）外用于游离的巨核细胞，以-42 mV的保持电位诱导大的向内电流（振幅100-500 pA），并在1秒内完全失活。ADP诱导电流的振幅在超极化时变大，而在去极化时变小，并在0 mV左右极性反转向外。整体的I-V关系呈现向内整流。在等渗Ca2+或Ba2+或Mg2+溶液中也观察到ADP诱导的内向电流，这表明ADP激活的通道对这些二价阳离子是可调节的。这些通道也可渗透到一价阳离子，如Na+、K+或Cs+。这些表明，某种类型的嘌呤能受体专门参与巨核细胞中产生快速阳离子电流，其功能特性与大脑中描述的5-羟色胺受体非常相似。

In dentate gyrus of the rat hippocampal slices, principal neurons (granule cells) and local inhibitory neurons (basket cells) identified under Namarsky microscopy. The effects of serotonin (5-HT) on these neurons were investigated using the whole-cell patch clamp technique and rapid perfusion (Y-tube) method. In granule cells, external application of 5-HT (0.2-100 uM) did not evoke any current but in basket cells definite inward currents at a holding potential of -63mV were induced. The I-V relation for 5-HT response showed a reversal potential around 0 mV accompanying a negative slope conductance at potentials below -60mV.To compare the functional proparties of these 5-HT receptors, newly identified ADP (adenosine-5'-diphosphate) receptors in the megakaryocytes from the mouse bone marrow were studied. When Cs^+ was used as a major internal cation to block K-currents, external application of ADP (10-100 uM) to dissociated megakaryocytes induced large inward currents (amplitude of 100-500 pA) at a holding potential of -42 mV,which showed a rapid decay with a complete inactivation in 1 sec.The amplitude of the ADP-induced currents became larger when hyperpolarized, while it became smaller by depolarization and reversed its polarity to outward at aroudn 0 mV.The overall I-V relationship showed an inward rectification. The ADP-induced inward currents are also observed in isotonic Ca2+ or Ba2+ or Mg2+ solution, which indicates that the channels activated by ADP are pormeable to these divalent cations. The channels are also permeable to monovalent cations such as Na+, K+ or Cs+.These indicate that a certain type of purinergic receptor is specifically involved in generating rapid cationic currents in megakaryocytes, the functional properties of which are very similar to those described for the 5-HT receptors in the brain.