Intrinsic theta-frequency membrane potential oscillations in hippocampal CA1 interneurons of stratum lacunosum-moleculare

被引:112
作者
Chapman, CA
Lacaille, JC
机构
[1] Univ Montreal, Fac Med, Dept Physiol, Montreal, PQ H3C 3J7, Canada
[2] Univ Montreal, Ctr Rech Sci Neurol, Montreal, PQ H3C 3J7, Canada
关键词
D O I
10.1152/jn.1999.81.3.1296
中图分类号
Q189 [神经科学];
学科分类号
071006 ;
摘要
The ionic conductances underlying membrane potential oscillations of hippocampal CA1 interneurons located near the border between stratum lacunosum-moleculare and stratum radiatum (LM) were investigated using H hole cell current-clamp recordings in rat hippocampal slices. At 22 degrees C, when LM cells were depolarized near spike threshold by current injection, 91% of cells displayed 2-5 Hz oscillations in membrane potential, which caused rhythmic firing. At 32 degrees C, mean oscillation frequency increased to 7.1 Hz. Oscillations were voltage dependent and H ere eliminated by hyperpolarizing cells 6-10 mV below spike threshold. Blockade of ionotropic glutamate and GABA synaptic transmission did not affect oscillations, indicating that they were not synaptically driven. Oscillations were eliminated by tetrodotoxin, suggesting that Na+ currents generate the depolarizing phase of oscillations. Oscillations were not affected by blocking Ca2+ currents with Cd2+ or Ca2+-free ACSF or by blocking the hyperpolarization-activated current (I-b) with Cs+ Both Ba2+ and a low concentration of 4-aminopyridine (4-AP) reduced oscillations but TEA did not. Theta-frequency oscillations were much less common in interneurons located in stratum oriens. Intrinsic membrane potential oscillations in LM cells of the CA1 region thus involve an interplay between inward Na+ currents and outward K+ currents sensitive to Ba2+ and 4-AP. These oscillations may participate in rhythmic inhibition and synchronization of pyramidal neurons during theta activity in vivo.
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页码:1296 / 1307
页数:12
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