Abstract
Electrophysiological properties of primary afferent neurons have been investigated by using dorsal root ganglion (DRG) neurons. It is well known that DRG neurons can be classified several subclasses on the basis of sensitivity to tetrodotoxin (TTX) and kinetic properties of Na+ currents. However, little is known about electrophysiological properties of gustatory neurons. In bullfrogs (Rana catesbeiana), afferents fibers transmitting gustatory information travel glossopharyngeal nerve. Cell bodies of glossopharyngeal nerve are located in glossopharyngeal nerve ganglion (GG). To investigate membrane properties of GG neuron, we applied patch clamp recordings to isolated GG neurons. GG neurons were retrogradely labeled with fluorescent dye Alexa Fluor dextran and whole cell patch clamp recordings were made from labeled neurons. In voltage-clamp recording condition, we recorded two subtypes of voltage-gated Na+ currents: TTX-sensitive and TTX-resistant Na+ currents. The neurons exhibiting TTX-sensitive Na+ currents had large cell membrane capacitance, whereas the neurons exhibiting TTX-resistant Na+ currents had small cell membrane capacitance. These results suggest that frog GG neurons consist of heterogeneous subpopulations. [J Physiol Sci. 2007;57 Suppl:S99]
