Microtransplantation of rat brain neurolemma into the plasma membrane of Xenopus laevis oocytes is an ex vivo method used to study channels and receptors in their native state using standard electrophysiological approaches. In this review, we show that oocytes injected with adult rat brain neurolemma elicited tetrodotoxin-sensitive inward ion currents upon membrane depolarization, which were increased in a concentration-dependent manner by treatment with the pyrethroid insecticides permethrin and deltamethrin. Under our initial protocols, oocyte health was reduced over time and neurolemma incorporation varied between batches of oocytes from different frogs, limiting the usefulness of the assay for regulatory issues. A collection of changes to the assay procedure, data acceptance criteria, and analysis method yield substantially improved precision and, hence, assay performance. These changes established this ex vivo approach as a toxicologically relevant assay to study the toxicodynamic action of pyrethroids on ion channels in their native state using neurolemma fragments prepared from juvenile and adult rat brains.