Figure 2. α-BgTx inhibition of ACh-evoked currents was direct and independent of Ca²⁺-induced Cl⁻ conductance.

ACh (20 μM)-evoked macroscopic currents in the presence or absence of α-BgTx (500 nM) were recorded with CsCH₃SO₄+ high EGTA internal solution (see Methods). The recorded currents were digitized, averaged and analysed. A, averaged currents evoked by ACh (20 μM) in neurones using CsCH₃SO₄ internal solution. B, averaged currents evoked by ACh +α-BgTx under the same conditions as in A. The time course of the current decay was faster than that recorded with standard internal solution. C, the t_½ values of the decay phase of the currents were analysed with non-parametric methods and presented as box plots (see Methods). Comparison of t_½ of all ACh (20 μM)-evoked currents in the absence or presence of α-BgTx recorded under control conditions in standard internal solution or in CsCH₃SO₄+ EGTA internal solution revealed significant (P≤ 0.001) inhibition of ACh-evoked currents by α-BgTx whether or not Ca²⁺-activated Cl⁻ conductance was blocked. The number of neurones recorded are noted above each box plot.