Abstract:
Various aspects of social behavior are influenced by the
highly conserved corticotrophin-releasing factor (CRF)
family of peptides and receptors in the mammalian telencephalon.
This study has mapped and compared the telencephalic
distribution of the CRF receptors, CRF1 and
CRF2, and two of their ligands, CRF and urocortin 3,
respectively, in African mole-rat species with diametrically
opposed social behavior. Naked mole-rats live in large
eusocial colonies that are characterized by exceptional
levels of social cohesion, tolerance, and cooperation in
burrowing, foraging, defense, and alloparental care for the
offspring of the single reproductive female. Cape molerats
are solitary; they tolerate conspecifics only fleetingly
during the breeding season. The telencephalic sites at
which the level of CRF1 binding in naked mole-rats
exceeds that in Cape mole-rats include the basolateral amygdaloid nucleus, hippocampal CA3 subfield, and dentate
gyrus; in contrast, the level is greater in Cape molerats
in the shell of the nucleus accumbens and medial
habenular nucleus. For CRF2 binding, the sites with a
greater level in naked mole-rats include the basolateral
amygdaloid nucleus and dentate gyrus, but the septohippocampal
nucleus, lateral septal nuclei, amygdalostriatal
transition area, bed nucleus of the stria terminalis, and
medial habenular nucleus display a greater level in Cape
mole-rats. The results are discussed with reference to
neuroanatomical and behavioral studies of various species,
including monogamous and promiscuous voles. By
analogy with findings in those species, we speculate that
the abundance of CRF1 binding in the nucleus accumbens
of Cape mole-rats reflects their lack of affiliative behavior.
