Fig. 5. CTN reduces Ca²⁺ currents from growth cones of isolated PeA neurons in L. stagnalis. (A) Representative Ca²⁺ (ruptured) whole-cell currents from a single transected growth cone (including adjacent neurite) without or with 50 µM scrambled CTN (srCTN) or CTN treatment. The currents were evoked from a holding potential of -100 mV and stepped from -60 mV to +80 mV at 10 mV increments, using a P/4 protocol. Currents were normalized by capacitance (pF). A phase-contrast imaging of a transected growth cone is shown in the insert at the bottom left. (B) Current density-voltage (I-V) plots from the traces in A. Peak current densities are smaller after CTN treatment compared to srCTN treatment and control conditions. The line represents a modified Boltzmann fit of the data, as described in Materials and methods and listed as G(pS/pF), Vrev (mV) and Vh (mV): control 0.34, 79 and 23; srCTN 0.27, 78 and 20; CTN 0.18, 80 and 40, respectively. (C) Average peak current density suggests that CTN significantly (P<0.05) reduces the peak current density in growth cones of PeA neurons. Data were obtained from five control (10.3±3.0 pA/pF), six srCTN (9.0±1.3 pA/pF) and five CTN (2.1±0.9 pA/pF) experiments. The data are presented as mean±s.e.m. Asterisk indicates significant difference (P<0.05) from the control condition.