DIFFERENTIAL-EFFECTS OF ZINC ON HYPERPOLARIZING AND DEPOLARIZING GABA(A) SYNAPTIC POTENTIALS IN HIPPOCAMPAL SLICE CULTURES

被引:6
作者
RICCIARDI, TN [1 ]
MALOUF, AT [1 ]
机构
[1] UNIV WASHINGTON, DEPT NEUROL SURG, SEATTLE, WA 98195 USA
关键词
HIPPOCAMPUS; SLICE CULTURE; ZINC; 4-AMINOPYRIDINE; GABA(A) DEPOLARIZING POTENTIAL; GABA(A) HYPERPOLARIZING POTENTIAL; EPILEPTIFORM ACTIVITY;
D O I
10.1016/0006-8993(95)00244-K
中图分类号
Q189 [神经科学];
学科分类号
071006 ;
摘要
We have examined the changes in GABA(A)-mediated synaptic potentials recorded from CA3 pyramidal neurons in hippocampal slice cultures following application of zinc (Zn2+). Unlike 4-AP, Zn2+ did not enhance fast hyperpolarizing potentials but primarily enhanced depolarizing GABA(A) potentials. Zn2+ did not alter the postsynaptic response of pyramidal neurons to pressure applied GABA, consistent with previous reports that Zn2+ enhances the release of GABA from presynaptic terminals. To examine the role of local circuitry in the production of Zn2+ responses, we recorded from cultures maintained for 7-10 days following removal of the dentate and hilus to allow complete degeneration of the messy fibers (DGX cultures). Zn2+ produced giant depolarizing potentials (GDPs) in DGX cultures that were identical to those in intact cultures. In contrast, the 4-AP response was dramatically altered in DGX cultures. In DGX cultures, Zn2+ co-applied with 4-AP appeared to inhibit the production of fast hyperpolarizing GABAA synaptic potentials produced by 4-AP alone. This inhibition of fast hyperpolarizing potentials suggests that Zn2+ may reduce the release of GABA onto pyramidal cell somata. These observations suggest that Zn2+ enhances GABA release from local circuit neurons that synapse onto pyramidal cell dendrites, and inhibits GABA release onto pyramidal cell somata.
引用
收藏
页码:80 / 87
页数:8
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