Bhandal, N.S., Ramsey, R.L., Harvey, R.J., Darlison, M.G. and Usherwood, P.N.R. (1995) Channel gating in the absence of agonist by a homooligomeric molluscan GABA receptor expressed inXenopus oocytes from a cloned cDNA. Invertebrate Neuroscience, 1 (3). pp. 267-272. 10.1007/BF02211028.
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We have previously described the isolation of a complementary DNA (cDNA) from the freshwater mollusc Lymnaea stagnalis encoding a polypeptide that exhibits approximately 50% identity to the beta-subunits of vertebrate gamma-aminobutyric acid (GABA) type A (GABAA) receptor. When expressed in Xenopus laevis oocytes from in vitro-transcribed RNA, the snail subunit forms functional homo-oligomeric receptors possessing chloride-selective ion channels. In recordings from voltage-clamped oocytes held at -60 mV, GABA induced an inward current, whereas application of the chloride-channel blocker picrotoxin (in the absence of agonist) elicited an apparent outward current. Single channel recordings obtained from cell-attached patches have revealed a single population of approximately 20 pS channels, with an open probability greater than 90% (at a pipette potential of -100 mV) in the absence of GABA. The relationship between single channel current and pipette potential was linear over the studied range (-100 mV to +60 mV), but the open probability was less for hyperpolarizations than for depolarizations. The spontaneous channel openings were blocked by micromolar concentrations of picrotoxin. Functional hetero-oligomeric receptors were formed when the molluscan subunit was co-expressed in oocytes with the bovine GABAA receptor alpha 1-subunit, but the channels gated by these receptors did not open spontaneously.
|Departments, units and centres:||Department of Pharmacology > Department of Pharmacology|
|Journal or Publication Title:||Invertebrate Neuroscience|
|Deposited By:||Library Staff|
|Deposited On:||01 Apr 2011 09:47|
|Last Modified:||16 Jun 2011 11:09|
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