Developmental vitamin D (DVD) deficiency alters pup-retrieval but not isolation-induced pup ultrasonic vocalizations in the rat Thomas H.J. Burne a,b, ⁎, Jonathan O'Loan b , Karisha Splatt b , Suzanne Alexander a,b , John J. McGrath a,b,c , Darryl W. Eyles a,b a Queensland Brain Institute, The University of Queensland, Brisbane, Queensland 4072, Australia b Queensland Centre for Mental Health Research, The Park Centre for Mental Health, Wacol, Queensland 4076, Australia c Department of Psychiatry, The University of Queensland, Brisbane, Queensland 4072, Australia abstract article info Article history: Received 15 July 2010 Received in revised form 1 November 2010 Accepted 1 November 2010 Keywords: Maternal behaviour Development Sprague–Dawley rats Ultrasonic vocalization Vitamin D 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 D 3 , 1,25 (OH) 2 D 3 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. © 2010 Elsevier Inc. All rights reserved. 1. Introduction There is now robust evidence from in vitro and whole animal studies showing that low vitamin D levels during early life affect brain development and adult behaviour in rats [5,12] and in mice [15]. For example, rats exposed to transient developmental vitamin D (DVD) deficiency show altered locomotion in the open field [3–5,13], and are particularly sensitive to the locomotor inducing effects of the N-methyl- D-aspartate receptor (NMDA) antagonist, MK-801 [19]. Furthermore, DVD-deficient animals were selectively sensitive to the locomotion- retarding effects of haloperidol [19]. Thus, the enhanced sensitivity to an NMDA antagonist and a dopamine (DA) D 2 receptor antagonist suggests dysregulation of (at least) dopaminergic and glutamatergic pathways in the DVD-deficient adult. Altered pup ultrasonic vocalizations have been reported after a variety of prenatal exposures such as stress [23], iron deficiency [11] and foetal alcohol syndrome [21]. However, there are several studies implicating dopaminergic pathways in ultrasonic vocalizations in neonate [10,25–27] and adult rats [2]. We have shown that the expression of co-methyl transferase (COMT) and the ratio of the major dopamine (DA) metabolites, homovanilic acid (HVA) and 3,4- dihydroxyphenylacetic acid (DOPAC) were altered in the forebrain of DVD-deficient rats on the day of birth [20]. Taken together, these data indicate that DVD-deficiency is associated with altered dopaminergic turnover in the neonatal rat. However, we do not know if these changes are associated with altered behaviour in the neonate. The mechanisms leading to the distinctive adult behavioural phenotype of the DVD model remain to be determined. It is clear that the pups differ from birth — neonatal rats born to DVD-deficient dams have enlarged ventricles, a thinner cortex and an increase in cell proliferation [8,12]. It remains to be clarified if postnatal factors related to maternal care could also contribute to the phenotype [22]. It can be a challenge to explore these issues because it is feasible that (a) vitamin D deficiency during pregnancy may alter maternal be- haviour on the day of birth, or (b), altered pup behaviour may elicit altered maternal behaviour, which could subsequently amplify any developmental deviance. In order to explore the effect of vitamin D deficiency on pup/maternal behaviour we have examined two measures relevant to dam–pup interactions; (a) neonatal behaviour was assessed by isolation-induced ultrasonic vocalizations and (b) maternal behaviour was assessed using a pup-retrieval test on the day of birth. We hypothesized that DVD- Physiology & Behavior 102 (2011) 201–204 ⁎ Corresponding author. Queensland Brain Institute, The University of Queensland, Brisbane, Queensland 4072, Australia. Tel.: + 61 7 33466371; fax: + 61 7 33466424. E-mail address: t.burne@qcmhr.uq.edu.au (T.H.J. Burne). 0031-9384/$ – see front matter © 2010 Elsevier Inc. All rights reserved. doi:10.1016/j.physbeh.2010.11.006 Contents lists available at ScienceDirect Physiology & Behavior journal homepage: www.elsevier.com/locate/phb