Figure 6.

Inhibition of hyperpolarization to ACh or NS309 upon loss of electrical conduction. (A) Control V_m responses at Site 1 (V_m1) and Site 2 (V_m2) to ±0.1–3 nA injected at Site 1 followed by treatment with 40 µM βGA. Note ∼20 mV hyperpolarization during βGA followed by loss of V_m2 responses coincident with increased V_m1. The latter effect reflects greater input resistance during current injection. (B) Control response to ACh at Site 2 before current injections; note transient hyperpolarization during continuous exposure to ACh. (C) Recording at Site 2 in the presence of βGA after loss of electrical conduction in A. After 6–7 min of exposure to βGA, note depolarization to < −10 mV and lack of hyperpolarization to ACh; recording is representative of n= 5 with 40 µM βGA and n= 3 with 100 µM CBX. (D) Control V_m responses at Site1 (V_m1) and Site 2 (V_m2) to ±0.1–1 nA injected at Site 1 followed by treatment with 100 µM CBX. During CBX treatment, note transient ∼20 mV hyperpolarization followed by loss of V_m2 responses (small residual capacitance spikes remain). Coincident increase of V_m1 responses reflects greater input resistance during current injection. (E) Response to NS309 at Site 2 before current injections. Note sustained hyperpolarization during exposure to NS309 versus transient response to ACh in B. Hyperpolarization to NS309 reversed within 10 min after washout (not shown). (F) Recording at Site 2 in the presence of CBX after loss of electrical conduction in A. After 6–7 min of exposure to CBX, note depolarization to −10 mV and lack of hyperpolarization to NS309; recording is representative of n= 4 with 100 µM CBX and n= 8 with 40 µM βGA. Reference to ‘out’ on V_m recordings in C and F illustrates withdrawal of microelectrode from cell, confirming stability of intracellular recording throughout these experiments.