A potentially novel nicotinic receptor in Aplysia neuroendocrine cells

被引:10
作者
White, Sean H. [1 ]
Carter, Christopher J. [1 ]
Magoski, Neil S. [1 ]
机构
[1] Queens Univ, Dept Biomed & Mol Sci Phys Grad Program, Ctr Neurosci, Kingston, ON K7L 3N6, Canada
基金
加拿大健康研究院;
关键词
acetylcholine receptor; alpha-conotoxin ImI; Ca2+ permeability; desensitization; mollusc; MULTIPLE SEQUENCE ALIGNMENT; NONSELECTIVE CATION CHANNEL; DOUBLE-STRANDED-RNA; GATED ION CHANNELS; ACETYLCHOLINE-RECEPTOR; PHARMACOLOGICAL-PROPERTIES; PROLONGED DEPOLARIZATION; BAG CELLS; BINDING; NEURONS;
D O I
10.1152/jn.00796.2013
中图分类号
Q189 [神经科学];
学科分类号
071006 ;
摘要
Nicotinic receptors form a diverse group of ligand-gated ionotropic receptors with roles in both synaptic transmission and the control of excitability. In the bag cell neurons of Aplysia, acetylcholine activates an ionotropic receptor, which passes inward current to produce a long-lasting afterdischarge and hormone release, leading to reproduction. While testing the agonist profile of the cholinergic response, we observed a second current that appeared to be gated only by nicotine and not acetylcholine. The peak nicotine-evoked current was markedly smaller in magnitude than the acetylcholine-induced current, cooperative (Hill value of 2.7), had an EC50 near 500 mu M, readily recovered from desensitization, showed Ca2+ permeability, and was blocked by mecamylamine, dihydro-beta-erythroidine, or strychnine, but not by alpha-conotoxin ImI, methyllycaconitine, or hexamethonium. Aplysia transcriptome analysis followed by PCR yielded 20 full-length potential nicotinic receptor subunits. Sixteen of these were predicted to be cation selective, and real-time PCR suggested that 15 of the 16 subunits were expressed to varying degrees in the bag cell neurons. The acetylcholine-induced current, but not the nicotine current, was reduced by double-strand RNA treatment targeted to both subunits ApAChR-C and -E. Conversely, the nicotine-evoked current, but not the acetylcholine current, was lessened by targeting both subunits ApAChR-H and -P. To the best of our knowledge, this is the first report suggesting that a nicotinic receptor is not gated by acetylcholine. Separate receptors may serve as a means to differentially trigger plasticity or safeguard propagation by assuring that only acetylcholine, the endogenous agonist, initiates large enough responses to trigger reproduction.
引用
收藏
页码:446 / 462
页数:17
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