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Ca channels induced in Xenopus oocytes by rat brain mRNA

Leonard, John P. and Nargeot, Joël and Snutch, Terry P. and Davidson, Norman and Lester, Henry A. (1987) Ca channels induced in Xenopus oocytes by rat brain mRNA. Journal of Neuroscience, 7 (3). pp. 875-881. ISSN 0270-6474. PMCID PMC6569056.

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RNA was isolated from brains of 16-d-old rats and poly(A) samples were injected into stage V and VI oocytes. After allowing 2–5 d for expression, most oocytes were exposed to medium in which the K had been replaced by Cs for 24 hr prior to recording. Ba currents were usually measured in Cl-free Ba-methanesulfonate saline. I_(Ba) in noninjected oocytes was often undetectable, but ranged up to 50 nA (22 ± 4 nA, n = 21). In contrast, injected oocytes showed a peak I_(Ba) of 339 ± 42 nA (n = 33). The threshold for activation of I_(Ba) was -40 mV, with peak currents at +10 to +20 mV. After a peak, currents decayed to a nearly steady level along a single-exponential time course (τ = 650 ± 50 msec at +20 mV). The maintained current was 67 ± 6% (n = 9) of the early peak amplitude. A prepulse duration of 5 sec was needed to examine the inactivation of barium currents in injected oocytes. The inward I_(Ba) could be observed in BaCl₂ solutions at potentials positive to E_(Cl) and also in Na-free salines, indicating that neither Cl⁻ nor Na⁺ was carrying the inward current. Although I_(Ba) displayed voltage- independent blockade by Cd (50% inhibition at 6 µM), the peptide Ca channel antagonist, ω-CgTX (1 µM), and the organic Ca channel-blocking agents (verapamil, compound W-7, and nifedipine) were uniformly ineffective. No effects were observed with the dihydropyridine antagonist nifedipine (even at 10 µM, or when cells were held at -40 mV) or agonist Bay K-8644. However, I_(Ba) was enhanced via activation of protein kinase C with 4-beta-phorbol dibutyrate (PBT₂). In contrast, use of forskolin to activate protein kinase A did not alter I_(Ba). However, experiments in the presence of Cd revealed that forskolin decreased I_K. Ca channels produced by rat brain mRNA were thus in contrast to the nifedipine-sensitive, Bay K-8644- and forskolin-enhanced Ca channels observed after injection of rat heart mRNA (Dascal et al., 1986).

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Lester, Henry A.0000-0002-5470-5255
Additional Information:© 1987 by Society for Neuroscience. Beginning six months after publication the Work will be made freely available to the public on SfN’s website to copy, distribute, or display under a Creative Commons Attribution 4.0 International (CC BY 4.0) license ( Received June 20, 1986; accepted Sept. 13, 1986. We thank N. Dascal, D. S. Krafte, and R. J. Miller for helpful suggestions. This research was supported by fellowships from the American Heart Association, Greater Los Angeles Affiliate (to J.L. and T.S.), the Conseil de recherches en sciences naturelles et en genie du Canada (to T.S.), and the National Institutes of Health (Grants GM-10991 and GM-29836).
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American Heart Association, Greater Los Angeles AffiliateUNSPECIFIED
Natural Sciences and Engineering Research Council of Canada (NSERC)UNSPECIFIED
Issue or Number:3
PubMed Central ID:PMC6569056
Record Number:CaltechAUTHORS:20201013-145241336
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Official Citation:Ca channels induced in Xenopus oocytes by rat brain mRNA JP Leonard, J Nargeot, TP Snutch, N Davidson, HA Lester Journal of Neuroscience 1 March 1987, 7 (3) 875-881; DOI: 10.1523/JNEUROSCI.07-03-00875.1987
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:106041
Deposited By: George Porter
Deposited On:13 Oct 2020 22:37
Last Modified:13 Oct 2020 22:37

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