Electrophysiological effects of a neurotoxin extracted from the skin of the Australian frog Pseudophryne coriacea

Abstract

1. The electrophysiological effects of a pumiliotoxin-B-like alkaloid extracted from the skin of the Australian frog Pseudophryine coriacea (PsC) have been studied in rat superior cervical ganglia at 37°C. 2. PsC (50 mg/ml) elicits a broadening of the evoked compound action potential and, at rest, the appearance of spontaneous spike discharge at 10–20 Hz. Action potentials presumably originate far away from the soma, which is invaded in a typical ISSD sequence. 3. The toxin effect is not related to any direct action on the preganglionic fibers of the sympathetic trunk, and does not involve synaptic mechanisms. 4. Two-electrode voltage-clamp experiments showed that the main properties of the major voltage-dependent ionic currents are apparently unaffected by the toxin, while the cell input resistance is considerably reduced. 5. The data are consistent with the hypothesis that PsC elicits a cationic permeability increase generating a pacemaker current in a region close to the cell soma.