2 TRANSIENT OUTWARD CURRENTS IN HISTAMINE NEURONS OF THE RAT HYPOTHALAMUS INVITRO
2 TRANSIENT OUTWARD CURRENTS IN HISTAMINE NEURONS OF THE RAT HYPOTHALAMUS INVITRO
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DOI：
10.1113/jphysiol.1990.sp017905
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发表时间：
1990-01-01
影响因子：
5.5
通讯作者：
REINER, PB
中科院分区：
文献类型：
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作者：
GREENE, RW;HAAS, HL;REINER, PB
用单电极电压钳技术，在大鼠下丘脑脑片上研究了结节乳头核组胺能神经元的瞬时外向电流。在静息电位下，瞬时外向电流呈现稳态失活状态。通过V1/2为-85.+-的超极化来解除失活。1.2 mV，激活的V1/2为-60.3.+-。2.1 mV。暂态外向电流的衰减可以用两个时间常数为104.+-的指数进行最佳拟合。36和568+-。128毫秒。这两个分量暂称为IA，f和IA，S，分别表示快衰减电流和慢衰减电流。失活的去除是时间依赖的；通过200ms或更长持续时间的-110 mV的超极化脉冲完全去除失活。超极化预脉冲50ms或更大时，IA、f的失活消失较快，而超极化预脉冲持续时间为200ms时，S的失活才完全消失。快速衰减电流Ia，f可被1 mM-4-氨基吡啶选择性阻断。四乙基氯化铵(10 MM)对IA，f和IA，S均无影响。IA，S的失活曲线，由计算的慢指数函数的幅值和1 mM的4-氨基吡啶的剩余电流测得，均为IA，f的负值。同样，IA，S的激活曲线与IA，f呈正相关。IA、S在含2.5 mM-K+的介质中的逆转电位为-95.+-。结论：组胺能结节乳头神经元至少具有两种瞬时外向电流，可根据其衰减率、4-氨基吡啶敏感性、电压依赖性和翻转电位加以区分。
The transient outward current exhibited by the histamine neurones of the tuberomammillary nucleus was studied using the single-electrode voltage clamp technique in an in vitro rat hypothalamic slice preparation. The transient outward current exhibited steady-state inactivation at the resting potential. Inactivation was removed by priming hyperpolarization with a V1/2 of -85 .+-. 1.2 mV, while the V1/2 for activation was -60.3 .+-. 2.1 mV. The decay of the transient outward current was best fitted by two exponentials with time constants of 104 .+-. 36 and 568 .+-. 128 ms. These two components were provisionally termed IA,f and IA,S for the fast and slowly decaying currents, respectively. Removal of inactivation was time dependent; inactivation was fully removed by hyperpolarizing pulses to -110 mV of 200 ms or greater duration. Removal of inactivation of IA,f was rapid, becoming complete with hyperpolarizing pre-pulses of 50 ms or greater, while removal of inactivation of IA,S was not complete until hyperpolarizing pre-pulses were 200 ms in duration. The fast decaying current IA,f was selectively blocked by 1 mM-4-aminopyridine. Tetraethylammonium chloride (10 mM) had no effect on either IA,f or IA,S. The inactivation curves for IA,S; determined both by using the values obtained from the amplitude of the computed slower exponential function as well as that of the current remaining in 1 mM 4-aminopyridine, were negative to those of IA,f. Similarly derived activation curves for IA,S were positive to those of IA,f. Superfusion with a nominal 0 Ca2+ medium containing 10 mM-Mg2+ did not reduce the maximal transient outward current. The reversal potential of IA,S with 2.5 mM-K+ in the medium was -95 .+-. 3 mV; the reversal potential of IA,f was at least 15 mV negative to that of IA,S. It is concluded that histaminergic tuberomammillary neurons possess at least two transient outward currents which can be distinguished on the basis of their rates of decay, 4-aminopyridine sensitivity, voltage dependence and reversal potentials.