Electrophysiological evidence for projections of myelinated and non-myelinated primary vagal afferents to the rat insular cortex.

Two types of vagal evoked potentials were recorded in chloralose-anesthetized rats: a positive-negative one and a negative-positive one in granular and agranular insular cortical subareas, respectively, the former being more susceptible to barbiturate. Both potentials consisted of two subtypes which were distinct as to threshold and latency. Peripheral conduction velocities as well as thresholds of these two subtypes corresponded to myelinated and non-myelinated primary afferents, respectively. Thus, these two primary vagal afferents are probably both represented in two insular cortical subareas, through pharmacologically distinct pathways.