Chromosome-scale genome assembly of the African giant pouched rat (Cricetomys ansorgei) and evolutionary analysis reveals evidence of olfactory specialization

Characterization of oxytocin and vasopressin receptors in the Southern giant pouched rat and comparison to other rodents

Vasopressin and oxytocin are well known and evolutionarily ancient modulators of social behavior. The distribution and relative densities of vasopressin and oxytocin receptors are known to modulate the sensitivity to these signaling molecules. Comparative work is needed to determine which neural networks have been conserved and modified over evolutionary time, and which social behaviors are commonly modulated by nonapeptide signaling. To this end, we used receptor autoradiography to determine the distribution of vasopressin 1a and oxytocin receptors in the Southern giant pouched rat (Cricetomys ansorgei) brain, and to assess the relative densities of these receptors in specific brain regions. We then compared the relative receptor pattern to 23 other species of rodents using a multivariate ANOVA. Pouched rat receptor patterns were strikingly similar to hamsters and voles overall, despite the variation in social organization among species. Uniquely, the pouched rat had dense vasopressin 1a receptor binding in the caudate-putamen (i.e., striatum), an area that might impact affiliative behavior in this species. In contrast, the pouched rat had relatively little oxytocin receptor binding in much of the anterior forebrain. Notably, however, oxytocin receptor binding demonstrated extremely dense binding in the bed nucleus of the stria terminalis, which is associated with the modulation of several social behaviors and a central hub of the social decision-making network. Examination of the nonapeptide system has the potential to reveal insights into species-specific behaviors and general themes in the modulation of social behavior.

Spontaneous Pituitary Neoplasm in Two Female Geriatric Southern Giant Pouched Rats (Cricetomys ansorgei)

Southern giant pouched rats (Cricetomys ansorgei) are a small muroid species native to the sub-Saharan Africa. Their exceptionally developed olfactory system, trainability, and relatively small size makes them useful working animals for various applications in humanitarian work. At our institution, a breeding colony of Southern giant pouched rats is maintained to study their physiology and utility as scent detectors. This case report describes the occurrence of spontaneous pituitary neoplasms with distinct clinical presentations in 2 geriatric (approximately 7.5 y old) wild-caught female Southern giant pouched rats. The first pouched rat displayed vestibular deficits, including left-sided head tilt, ataxia, disorientation, and circling. MRI revealed a large, focal heterogeneous mass arising from the pituitary fossa. The second pouched rat presented with polyuria, polydipsia, and hyperglycemia but no neurologic signs. Examination after euthanasia revealed a prolactin (PRL)-expressing pituitary carcinoma and adenoma in the first and second pouched rat, respectively, associated with mammary hyperplasia in both animals. This is the first report of spontaneous PRL-producing pituitary tumors in Southern giant pouched rats.