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The pharmacology of recombinant GABA A receptors containing bovine α 1 , β 1 , γ 2L sub‐units stably transfected into mouse fibroblast L‐cells
Author(s) -
Home A.L.,
Hadingham K.L.,
Macaulay A.J.,
Whiting P.,
Kemp J.A.
Publication year - 1992
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.1992.tb14515.x
Subject(s) - bicuculline , picrotoxin , zolpidem , gabaa receptor , chemistry , gaba receptor antagonist , flunitrazepam , agonist , receptor , pharmacology , extracellular , flurazepam , biophysics , benzodiazepine , biochemistry , biology , insomnia
1 Responses to γ‐aminobutyric acid (GABA) were evoked in mouse fibroblast L‐cells stably transfected with bovine, α 1 , β 1 , γ 2L sub‐units of the GABA A receptor. Expression was stimulated via a steroid‐inducible promoter system. 2 In near symmetrical intracellular and extracellular chloride concentrations, GABA evoked inward currents at negative holding potentials that reversed at + 5 mV and displayed slight outward rectification. Concentration‐response curves were fitted well by the logistic equation. GABA had a pEC 50 = 5.1 ± 0.1 and the curves had a slope of 1.9 ± 0.1 3 Responses to GABA were antagonized by bicuculline, picrotoxin and penicillin. The action of bicuculline was competitive (pA 2 = 6.4) whilst the block by picrotoxin was uncompetitive and strongly agonist‐dependent. 4 Benzodiazepine receptor agonists potentiated responses to 3 μ m GABA. The rank order of potency was FG 8205 > flunitrazepam > Zolpidem > C1218872. FG 8205 and C1218872 produced markedly lower maximal potentiations with efficacies 0.4 and 0.6 × that of flunitrazepam, respectively. The potencies of Zolpidem and C1218872 observed are in agreement with the BZ 1 type pharmacology of this sub‐unit combination. The potentiation of GABA by flunitrazepam was antagonized by flumazenil with a K i of 3.8 n m . 5 GABA responses were potentiated in the presence of pentobarbitone and alphaxalone. The response was also noticeably broadened by these compounds due to a decrease in the response decay rate. Concentrations of pentobarbitone of 100 μ m and above evoked an inward current in the absence of GABA. Alphaxalone up to 10 μ m did not evoke a direct response. 6 This expression system produced functional receptors that behaved in a fashion analogous to those found endogenously in other preparations. Thus, this system appears to provide a useful and versatile preparation for the analysis of sub‐unit regulation of GABA A receptor pharmacology.