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Namarsky显微镜下，在大鼠海马脑片齿状回中，主要神经元（颗粒细胞）和局部抑制性神经元（篮细胞）被识别。应用全细胞膜片钳技术和快速灌流（Y管）法观察5-羟色胺（5-HT）对这些神经元的作用。在颗粒细胞中，外源性5-HT（0.2-100 μ M）不引起任何电流，而在篮状细胞中，在保持电位为-63mV时，可引起明确的内向电流。5-HT反应的I-V关系在0 mV附近出现反转电位，在-60mV以下出现负斜率电导。为了比较这些5-HT受体的功能前体，我们研究了小鼠骨髓巨核细胞中新鉴定的ADP（adenosine-5 '-diphosphate）受体。当Cs^+作为主要的内阳离子阻断K电流时，（10-100 μ M）诱导巨核细胞产生大的内向电流（幅度为100-500 pA），在保持电位为-42 mV时，该电流迅速衰减，1秒内完全失活。在0 mV左右，除极使其变小，极性反转为外向，I-V关系呈内向整流。在等渗的Ca ~（2+）、Ba ~（2+）或Mg ~（2+）溶液中也观察到ADP诱导的内向电流，表明ADP激活的通道对这些二价阳离子是可渗透的。这些通道对Na+、K+或Cs+等一价阳离子也具有渗透性，这表明在巨核细胞中有一种特定类型的嘌呤能受体特异性地参与产生快速阳离子电流，其功能特性与脑中5-HT受体的功能特性非常相似。

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.