Bicuculline blocks nicotinic acetylcholine response in isolated intermediate lobe cells of the pig

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Abstract
1 The effect of bicuculline on nicotinic acetylcholine (ACh) responses in isolated intermediate lobe (IL) cells of the pig was investigated by use of patch-clamp techniques. Bicuculline was found to reduce AChevoked whole-cell currents (IACh) in all cells tested (n = 40). 2 The blocking effect of bicuculline on IACh was dose-dependent, the concentration producing half-maximal blockade being 43.8 μm. 3 The blockade of IACh by bicuculline was not voltage-dependent at membrane potentials above −60 mV, but a slight voltage-dependence was observed at holding potentials (HP) of −80 and −100 mV. 4 The inhibitory effect of bicuculline on IACh was partially competitive at a HP of −60 mV. 5 Neither SR 95531, a pyridazinyl γ-aminobutyric acid derivative, nor t-butylbicyclophosphorothionate (TBPS) blocked IACh in IL cells. 6 It is concluded that bicuculline interacts directly with the ACh receptor-ionophore complex on porcine IL cells.