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Zahratka JA, Williams PDE, Summers PJ, Komuniecki RW, Bamber BA. Serotonin differentially modulates Ca2+ transients and depolarization in a C. elegans nociceptor. J Neurophysiol 2014; 113:1041-50. [PMID: 25411461 DOI: 10.1152/jn.00665.2014] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Monoamines and neuropeptides modulate neuronal excitability and synaptic strengths, shaping circuit activity to optimize behavioral output. In C. elegans, a pair of bipolar polymodal nociceptors, the ASHs, sense 1-octanol to initiate escape responses. In the present study, 1-octanol stimulated large increases in ASH Ca(2+), mediated by L-type voltage-gated Ca(2+) channels (VGCCs) in the cell soma and L-plus P/Q-type VGCCs in the axon, which were further amplified by Ca(2+) released from intracellular stores. Importantly, 1-octanol-dependent aversive responses were not inhibited by reducing ASH L-VGCC activity genetically or pharmacologically. Serotonin, an enhancer of 1-octanol avoidance, potentiated 1-octanol-dependent ASH depolarization measured electrophysiologically, but surprisingly, decreased the ASH somal Ca(2+) transients. These results suggest that ASH somal Ca(2+) transient amplitudes may not always be predictive of neuronal depolarization and synaptic output. Therefore, although increases in steady-state Ca(2+) can reliably indicate when neurons become active, quantitative relationships between Ca(2+) transient amplitudes and neuronal activity may not be as straightforward as previously anticipated.
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Affiliation(s)
- Jeffrey A Zahratka
- Department of Biological Sciences, The University of Toledo, Toledo, Ohio
| | - Paul D E Williams
- Department of Biological Sciences, The University of Toledo, Toledo, Ohio
| | - Philip J Summers
- Department of Biological Sciences, The University of Toledo, Toledo, Ohio
| | | | - Bruce A Bamber
- Department of Biological Sciences, The University of Toledo, Toledo, Ohio
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Liu Y, Zhang H, Huang D, Qi J, Xu J, Gao H, Du X, Gamper N, Zhang H. Characterization of the effects of Cl⁻ channel modulators on TMEM16A and bestrophin-1 Ca²⁺ activated Cl⁻ channels. Pflugers Arch 2014; 467:1417-1430. [PMID: 25078708 DOI: 10.1007/s00424-014-1572-5] [Citation(s) in RCA: 65] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2014] [Revised: 06/13/2014] [Accepted: 06/30/2014] [Indexed: 11/30/2022]
Abstract
The Ca(2+) activated Cl(-) channels (CaCCs) play a multitude of important physiological functions. A number of candidate proteins have been proposed to form CaCC, but only two families, the bestrophins and the TMEM16 proteins, recapitulate the properties of native CaCC in expression systems. Studies of endogenous CaCCs are hindered by the lack of specific pharmacology as most Cl(-) channel modulators lack selectivity and a systematic comparison of the effects of these modulators on TMEM16A and bestrophin is missing. In the present study, we studied seven Cl(-) channel inhibitors: niflumic acid (NFA), NPPB, flufenamic acid (FFA), DIDS, tannic acid, CaCCinh-A01 and T16Ainh-A01 for their effects on TMEM16A and bestrophin-1 (Best1) stably expressed in CHO (Chinese hamster ovary) cells using patch clamp technique. Among seven inhibitors studied, NFA showed highest selectivity for TMEM16A (IC50 of 7.40 ± 0.95 μM) over Best1 (IC50 of 102.19 ± 15.05 μM). In contrast, DIDS displayed a reverse selectivity inhibiting Best1 with IC50 of 3.93 ± 0.73 μM and TMEM16A with IC50 of 548.86 ± 25.57 μM. CaCCinh-A01 was the most efficacious blocker for both TMEM16A and Best1 channels. T16Ainh-A01 partially inhibited TMEM16A currents but had no effect on Best1 currents. Tannic acid, NPPB and FFA had variable intermediate effects. Potentiation of channel activity by some of these modulators and the effects on TMEM16A deactivation kinetics were also described. Characterization of Cl(-) channel modulators for their effects on TMEM16A and Best1 will facilitate future studies of native CaCCs.
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Affiliation(s)
- Yani Liu
- Key Laboratory of Neural and Vascular Biology, Ministry of Education; Key Laboratory of New Drug Pharmacology and Toxicology, Hebei Province; Department of Pharmacology, Hebei Medical University, Shijizhuang, Heibei, China
| | - Huiran Zhang
- Key Laboratory of Neural and Vascular Biology, Ministry of Education; Key Laboratory of New Drug Pharmacology and Toxicology, Hebei Province; Department of Pharmacology, Hebei Medical University, Shijizhuang, Heibei, China
| | - Dongyang Huang
- Key Laboratory of Neural and Vascular Biology, Ministry of Education; Key Laboratory of New Drug Pharmacology and Toxicology, Hebei Province; Department of Pharmacology, Hebei Medical University, Shijizhuang, Heibei, China
| | - Jinlong Qi
- Key Laboratory of Neural and Vascular Biology, Ministry of Education; Key Laboratory of New Drug Pharmacology and Toxicology, Hebei Province; Department of Pharmacology, Hebei Medical University, Shijizhuang, Heibei, China
| | - Jiaxi Xu
- Key Laboratory of Neural and Vascular Biology, Ministry of Education; Key Laboratory of New Drug Pharmacology and Toxicology, Hebei Province; Department of Pharmacology, Hebei Medical University, Shijizhuang, Heibei, China
| | - Haixia Gao
- Key Laboratory of Neural and Vascular Biology, Ministry of Education; Key Laboratory of New Drug Pharmacology and Toxicology, Hebei Province; Department of Pharmacology, Hebei Medical University, Shijizhuang, Heibei, China
| | - Xiaona Du
- Key Laboratory of Neural and Vascular Biology, Ministry of Education; Key Laboratory of New Drug Pharmacology and Toxicology, Hebei Province; Department of Pharmacology, Hebei Medical University, Shijizhuang, Heibei, China
| | - Nikita Gamper
- Key Laboratory of Neural and Vascular Biology, Ministry of Education; Key Laboratory of New Drug Pharmacology and Toxicology, Hebei Province; Department of Pharmacology, Hebei Medical University, Shijizhuang, Heibei, China.,School of Biomedical Sciences, Faculty of Biological Sciences, University of Leeds, Leeds, UK
| | - Hailin Zhang
- Key Laboratory of Neural and Vascular Biology, Ministry of Education; Key Laboratory of New Drug Pharmacology and Toxicology, Hebei Province; Department of Pharmacology, Hebei Medical University, Shijizhuang, Heibei, China.
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