Variation in the permeability properties of the inhibitory post-synaptic membrane of the crayfish neuromuscular junction when activated by different concentrations of GABA
1. The membrane conductance of the crayfish muscle was measured with intracellular micro-electrodes. Increase in the membrane conductance induced by various concentrations of γ-amino butyric acid (GABA) was measured in the Br-, NO3-, I- and CNS- solutions and compared with that in Cl- solution. When the membrane was activated by lower concentrations of GABA, the resulting membrane conductance in NO3- and I- solutions was larger than in Cl- solution, while the membrane conductance activated by higher concentrations in NO3- and I- solutions were smaller than in Cl- solution. The membrane conductance activated by GABA was larger in Br- solution and smaller in CNS- solution than the membrane conductance activated in Cl- solution, throughout the concentration range of GABA examined.