Oxytocin-immunoreactive Neurons in the Paraventricular Nucleus of the Hypothalamus in Hetercephalus glaber: A Quantitative Analysis

The naked mole-rat (Heterocephalus glaber) demonstrates a strict social and reproductive hierarchy. Oxytocin (OXT) is a peptide hormone that acts both peripherally and centrally in the regulation of a number of sexual and social behaviours. The main area of central production of this peptide is the paraventricular nucleus of the hypothalamus (PVN). The present study characterized differences that exist in OXT neurons in this region. Breeders and subordinates from established colonies were sacrificed and brains were processed for OXT-immunoreactivity. Four further groups of paired animals underwent various social and hormonal manipulations (opposite-sex paired, same sex-paired, opposite-sex/gonadectomised paired, opposite-sex/vasectomized paired) and were also used for analysis. Results showed that subordinate naked mole-rats had significantly more OXT-immunoreactive neurons in the PVN than either breeders or paired animals that had been gonadectomised. However, no differences were found on measures of OXT cell volume. Possible functional significance of these differences is discussed.MAS