PCP4 immunoreactivity suggests the presence of hippocampal region CA2 in solitary, social and eusocial mole-rat species

Because African mole-rats express diverse social behaviors, they are prime candidates to study the effect of sociability on the evolution of brain circuits. This study compared the expression of Purkinje Cell Protein 4 (PCP4) in hippocampal slices of solitary Cape mole-rats, social Highveld mole-rats, and eusocial Damaraland and naked mole-rats. PCP4 is an established marker for pyramidal cells of hippocampal region CA2, a key structure for social memory and aggression. We observed prominent PCP4 immunoreactivity in the central part of the cornu Ammonis for all mole-rat species. While further verification is required, these findings suggest the extend of CA2 does not drastically differ despite varying social behaviors. Future studies may use this work as a starting point to explore the relationship between environmental requirements and the functional role of CA2.