Neuropeptide Receptor Transcript Expression Levels and Magnitude of Ionic Current Responses Show Cell Type-Specific Differences in a Small Motor Circuit
Neuropeptide Receptor Transcript Expression Levels and Magnitude of Ionic Current Responses Show Cell Type-Specific Differences in a Small Motor Circuit
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DOI：
10.1523/jneurosci.0171-15.2015
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发表时间：
2015-04-29
影响因子：
5.3
通讯作者：
Bucher, Dirk
中科院分区：
文献类型：
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作者：
Garcia, Veronica J.;Daur, Nelly;Bucher, Dirk
我们研究了北蟹的口胃神经节 (STG) 中神经肽受体转录表达和电流反应之间的关系。我们鉴定出与昆虫中的甲壳类心脏活性肽 (CCAP) 受体和哺乳动物神经肽 S 受体具有高度序列相似性的转录本。该转录本在整个神经系统中表达，与 CCAP 在一系列不同行为中的作用一致。在 STG 中，单细胞 qPCR 显示仅在一部分神经元中表达。该子集之前已被证明可以通过激活调制器激活的内向电流 (I-MI) 来响应 CCAP，但有一个例外。在一种显示表达但没有 I-MI 反应的细胞类型中，我们发现了突触电流的 CCAP 调节。 STG 神经元类型内的表达水平变化很大，但某些神经元类型之间存在显着差异。我们在两个确定的神经元（幽门外侧（LP）和心脏下（IC）神经元）中测试了 I-MI 对 CCAP 应用的反应的幅度和浓度依赖性。 LP 的表达量高出数倍，并显示出更大的电流响应。它还对低 CCAP 浓度更敏感，并在较低浓度下显示饱和，因为 S 形拟合显示更小的 EC50 值和更陡的斜率。此外，Proctolin（一种会聚到 I-MI 上的不同神经肽）的闭塞实验表明，饱和浓度的 CCAP 激活了 LP 中所有可用的 I-MI，但在 IC（受体转录物表达较低的神经元）中仅激活了大约三分之二。讨论了这些发现对共调制的影响。
We studied the relationship between neuropeptide receptor transcript expression and current responses in the stomatogastric ganglion (STG) of the crab, Cancer borealis. We identified a transcript with high sequence similarity to crustacean cardioactive peptide (CCAP) receptors in insects and mammalian neuropeptide S receptors. This transcript was expressed throughout the nervous system, consistent with the role of CCAP in a range of different behaviors. In the STG, single-cell qPCR showed expression in only a subset of neurons. This subset had previously been shown to respond to CCAP with the activation of a modulator-activated inward current (I-MI), with one exception. In the one cell type that showed expression but no I-MI responses, we found CCAP modulation of synaptic currents. Expression levels within STG neuron types were fairly variable, but significantly different between some neuron types. We tested the magnitude and concentration dependence of I-MI responses toCCAPapplication in two identified neurons, the lateral pyloric (LP) and the inferior cardiac (IC) neurons. LP had several-fold higher expression and showed larger current responses. It also was more sensitive to low CCAP concentrations and showed saturation at lower concentrations, as sigmoid fits showed smaller EC50 values and steeper slopes. In addition, occlusion experiments with proctolin, a different neuropeptide converging onto I-MI, showed that saturating concentrations of CCAP activated all available I-MI in LP, but only approximately two-thirds in IC, the neuron with lower receptor transcript expression. The implications of these findings for comodulation are discussed.