Opiate effects on rabbit vagus nerve: Electrophysiology and radioligand binding

Intracellular recordings were made from rabbit nodose ganglion cells in vitro. Morphine (up to 100 μM), normorphine (up to 10 μM) and d-Ala², Leu⁵-enkephalin (DADLE) (up to 5 μM) each had no detectable effect on the electrical properties of the cell membrane, except for local anesthetic-like actions at the highest concentrations which were not reversed by naloxone. Extracellular recordings were made from the infranodose vagus nerve in vitro using a sucrose gap method. No effects of morphine, normorphine or DADLE were detected on the resting potential, compound action potential or compound action potential enhanced by barium or tetraethylammonium. Moderate levels of stereospecific binding of tritiated dihydromorphine and DADLE were detected in both the nodose ganglion and vagus nerve. It is surmised that the radioligand binding sites on the nodose ganglion and vagus nerve are not functionally linked to detectable electrophysiological effects.