Functional characterization of cutaneous mechanoreceptor properties in aged rats

We investigated the effects of aging on rapidly (RA) and slowly adapting (SA) cutaneous mechanoreceptors by means of single fiber recordings and evoked sensory nerve action potentials (EAPs) of the hindpaw of the N. plantaris in adult and old Wistar rats. EAPs revealed comparable shapes and amplitudes in all animals of all age groups. In old rats, conduction velocities were slightly (15%) lengthened. The mechanoreceptor composition was different from adults, resulting in a lower number of SA units. We were not able to detect significant differences in the sizes of receptive fields and in the thresholds between old and adult animals. The absence of significant age-related changes in the cutaneous periphery of the hindpaw is discussed in respect to the previously reported alterations of cortical receptive field properties in old rats.