The site of action for the convulsant effect of pentylenetetrazol.

Abstract 1. Lymnaea neutons demonstrated convulsive bursting in response to 40 mM pentylenetetrazol (PTZ) applied extracellularly but showed no response to injections calculated to bring intracellular concentrations of PTZ to 100 mM. 2. PTZ was found to permeate cell membranes. 3. The site of the convulsive action of PTZ appears to be on the outer surface of the membrane.