Differences in spike train variability in rat vasopressin and oxytocin neurons and their relationship to synaptic activity
Differences in spike train variability in rat vasopressin and oxytocin neurons and their relationship to synaptic activity
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DOI：
10.1113/jphysiol.2006.123810
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发表时间：
2007-05-15
影响因子：
5.5
通讯作者：
Armstrong, William E.
中科院分区：
文献类型：
--
作者：
Li, Chunyan;Tripathi, Pradeep K.;Armstrong, William E.
大细胞神经分泌神经元的放电模式与激素释放密切相关，但突触与内在因素对尖峰时间分散的相对贡献尚不清楚。在本研究中，我们研究了放电模式的加压素（VP）和催产素（OT）视上神经元的冠状切片从处女雌性大鼠，有和没有封锁的抑制性和兴奋性突触电流。抑制性突触后电流（IPSC）是其兴奋性对应物（EPSC）的两倍，两者在OT中比VP神经元更普遍。催产素神经元在阈值附近放电比VP神经元慢且不规则。用印防己毒素阻断Cl-电流（包括强直电流和突触电流）可降低连续放电OT和VP神经元的峰间间期（ISI）变异性，而不改变输入电阻或放电速率。EPSC的阻断不影响击发模式。相性爆发神经元（推定VP神经元）不一致的影响广泛的突触阻滞，这表明内在因素可能占主导地位的ISI分布在此模式的切片。特异性阻断突触IPSC与gabazine也降低ISI的变化，但仅在OT神经元。在所有情况下，抑制性阻滞对放电模式的影响与输入电阻或放电频率的任何一致变化无关。由于绝大多数IPSC是随机分布的，在冠状切片的微型事件（mIPSC），这些研究结果意味着，即使mIPSC可以赋予不规则的OT神经元的放电模式，特别是，可能是重要的在体内调节尖峰模式。例如，哺乳期OT神经元爆发前的放电变异性增加可能与突触活动的显著变化有关。
The firing pattern of magnocellular neurosecretory neurons is intimately related to hormone release, but the relative contribution of synaptic versus intrinsic factors to the temporal dispersion of spikes is unknown. In the present study, we examined the firing patterns of vasopressin (VP) and oxytocin (OT) supraoptic neurons in coronal slices from virgin female rats, with and without blockade of inhibitory and excitatory synaptic currents. Inhibitory postsynaptic currents (IPSCs) were twice as prevalent as their excitatory counterparts (EPSCs), and both were more prevalent in OT compared with VP neurons. Oxytocin neurons fired more slowly and irregularly than VP neurons near threshold. Blockade of Cl- currents (including tonic and synaptic currents) with picrotoxin reduced interspike interval (ISI) variability of continuously firing OT and VP neurons without altering input resistance or firing rate. Blockade of EPSCs did not affect firing pattern. Phasic bursting neurons (putative VP neurons) were inconsistently affected by broad synaptic blockade, suggesting that intrinsic factors may dominate the ISI distribution during this mode in the slice. Specific blockade of synaptic IPSCs with gabazine also reduced ISI variability, but only in OT neurons. In all cases, the effect of inhibitory blockade on firing pattern was independent of any consistent change in input resistance or firing rate. Since the great majority of IPSCs are randomly distributed, miniature events (mIPSCs) in the coronal slice, these findings imply that even mIPSCs can impart irregularity to the firing pattern of OT neurons in particular, and could be important in regulating spike patterning in vivo. For example, the increased firing variability that precedes bursting in OT neurons during lactation could be related to significant changes in synaptic activity.