Developmental vitamin D (DVD) deficiency alters pup-retrieval but not isolation-induced pup ultrasonic vocalizations in the rat

Abstract Evidence from animal experiments now demonstrates that prenatal vitamin D levels influence brain development. The aims of this study were to examine isolation-induced pup ultrasonic vocalizations and maternal–infant interactions using a pup-retrieval test in developmental vitamin D (DVD) deficient and control rats. Sprague–Dawley rats were fed a vitamin D deficient diet or control diet six weeks prior to mating until birth and housed under UVB-free lighting conditions. In two separate experiments we recorded ultrasonic vocalizations at 46 KHz in isolated pups and we performed a pup-retrieval test on the day of birth. There was no significant effect of maternal diet on the calling rate of isolation-induced ultrasonic vocalizations by pups. We found that DVD-deficient dams retrieved their pups sooner than control dams and engaged in more pup directed activities (sniffing and carrying pups) and had a longer latency for self-grooming and rearing than control dams. We also assessed vitamin D related measures from a terminal blood sample immediately after the pup-retrieval test and found that DVD-deficient dams and pups had significantly lower levels of 25 OH D3 , 1, 25OH 2 D3 and phosphate, elevated levels of parathyroid hormone (PTH) but there was no significant effect of maternal diet on calcium levels. We speculate that the altered maternal–pup interactions identified in the DVD model may impact on early periods of brain development and behaviour.