Social condition and oxytocin neuron number in the hypothalamus of naked mole-rats (Heterocephalus glaber)

Social regulation of adult neurogenesis in a eusocial mammal

“…The status system and social organization of the naked mole-rat more closely resembles that of other cooperatively breeding species, in which dominant individuals have equivalent or higher basal GCs than subordinates (Creel, 2001). In addition to a potential role for GCs, elevated oxytocin production or output in subordinates (Mooney and Holmes, 2013) may stimulate neuronal growth, protecting against the suppressive effects of stress on hippocampal plasticity (Leuner et al, 2012). If GC levels truly do differ between dominant and subordinate naked mole-rats, our results may reflect a biphasic effect of stress on naked mole-rat neurobiology (Joels, 2006;2007).…”

“…Likewise, colonyhoused subordinates may become breeders if sexual suppression is lifted by a former breeder's death or removal (Margulis et al, 1995;Clarke and Faulkes, 1997). Though pronounced alterations in neural and endocrine functions accompany the change (Faulkes et al, 1990a;Margulis et al, 1995;Clarke and Faulkes, 1997;Seney et al, 2006;Holmes et al, 2008;Holmes et al, 2011;Mooney and Holmes, 2013), many or all subordinates are capable of transitioning to breeding status under the appropriate social conditions. This striking behavioural and physiological plasticity displayed by otherwise mature subordinates makes the naked mole-rat a prime candidate for the study of adult neurogenesis.…”

“…Naked mole-rats used in this study were also from a previous report (Mooney and Holmes, 2013). Subjects were dominant breeding adults between three and nine years of age, weighing 38 to 79 g, and subordinate adults between two and three years of age, weighing 33 to 79 g. As naked mole-rats typically reach adult body size within one year, can live for over 30 years in captivity, and do not show signs of aging well into their third decade (O'Riain and Jarvis, 1998;Buffenstein, 2005), the experimental animals were all young-aged adults.…”

“…All Breeders (n= 9; 4 male, 5 female) were gonadally-intact, and remained in their natal colonies for the duration of the experiment. Pairhoused animals were maintained in-colony prior to the experiment's initiation, at which time GDX animals were removed for surgery (see Mooney and Holmes, 2013) and allowed to recover. Then, all pair-housed animals were transferred to individual polycarbonate tubs with their appropriate cage mate and were maintained in their respective housing conditions for six months.…”

“…As the tissue used in this study was initially collected and processed in order to compare hypothalamic protein expression (Mooney and Holmes, 2013), anterior and posterior tissue was not available for all animals. Therefore, we were unable to quantify DCX expression in the SVZ/OB and ventral DG.…”