Early social isolation provokes electrophysiological and structural changes in cutaneous sensory nerves of adult male rats

Sensory and social deprivation from the mother and littermates during early life disturbs the development of the central nervous system, but little is known about its effect on the development of the periph- eral nervous system. To assess peripheral effects of early isolation, male rat pups were reared artificially in com- plete social isolation (AR); reared artificially with two same-age conspecifics (AR-Social); or reared by their mothers and with littermates (MR). As adults, the electro- physiological properties of the sensory sural (SU) nerve were recorded. We found that the amplitude and normal- ized area (with respect to body weight) of the compound action potential (CAP) response provoked by single elec- trical pulses of graded intensity in the SU nerves of AR animals were shorter than the CAP recorded in SU nerves from MR and AR-Social animals. The slope of the stimulus-response curve of AR SU nerves was smaller than that of the other nerves. The histological characteri- zation of axons in the SU nerves was made and showed that the myelin thickness of axons in AR SU nerves was significant lower (2-7mm) than that of the axons in the other nerves. Furthermore, the area and axon diameter of SU nerves of both AR and AR-Social animals were signifi- cant lower than in MR animals. This is the first report to show that maternal and littermate deprivation by AR dis- turbs the development of the myelination and electrophys- iological properties of axons in the SU nerve; the replacement of social cues prevents most of the effects. V C 2014 Wiley Periodicals, Inc. Develop Neurobiol 74: 1184- 1193, 2014