Gestational vitamin D deficiency and autism-related traits: the Generation R Study.

There is intense interest in identifying modifiable risk factors associated with autism-spectrum disorders (ASD). Autism-related traits, which can be assessed in a continuous fashion, share risk factors with ASD, and thus can serve as informative phenotypes in population-based cohort studies. Based on the growing body of research linking gestational vitamin D deficiency with altered brain development, this common exposure is a candidate modifiable risk factor for ASD and autism-related traits. The association between gestational vitamin D deficiency and a continuous measure of autism-related traits at ~6 years (Social Responsiveness Scale; SRS) was determined in a large population-based cohort of mothers and their children (n=4229). 25-hydroxyvitamin D (25OHD) was assessed from maternal mid-gestation sera and from neonatal sera (collected from cord blood). Vitamin D deficiency was defined as 25OHD concentrations less than 25 nmol l-1. Compared with the 25OHD sufficient group (25OHD>50 nmol l-1), those who were 25OHD deficient had significantly higher (more abnormal) SRS scores (mid-gestation n=2866, ß=0.06, P<0.001; cord blood n=1712, ß=0.03, P=0.01). The findings persisted (a) when we restricted the models to offspring with European ancestry, (b) when we adjusted for sample structure using genetic data, (c) when 25OHD was entered as a continuous measure in the models and (d) when we corrected for the effect of season of blood sampling. Gestational vitamin D deficiency was associated with autism-related traits in a large population-based sample. Because gestational vitamin D deficiency is readily preventable with safe, cheap and accessible supplements, this candidate risk factor warrants closer scrutiny.

Associations of maternal and fetal 25-hydroxyvitamin D levels with childhood lung function and asthma: the Generation R Study.

BACKGROUND: Exposure to low levels of vitamin D in fetal life might be a risk factor for childhood asthma. OBJECTIVE: We examined whether 25-hydroxyvitamin D levels in mid-gestation and at birth were associated with higher airway resistance and inflammation, and increased risks of wheezing and asthma in school-age children. METHODS: We performed a population-based prospective cohort study among 3130 mothers and their children. Maternal blood samples in mid-gestation and umbilical cord blood samples at birth were used to determine 25-hydroxyvitamin D levels. At age of 6, airway resistance (Rint) was measured by interrupter technique and airway inflammation by fractional exhaled nitric oxide (FENO) using NIOX chemiluminescence analyser. Wheezing and asthma were prospectively assessed by annual questionnaires until age 6. RESULTS: Maternal levels of 25-hydroxyvitamin D in mid-gestation were not associated with Rint, FeNO, wheezing patterns, or asthma. Children in the lowest tertile of 25-hydroxyvitamin D levels at birth had a higher Rint (Z-score (95% confidence interval [95% CI]): -0.42 (-0.84, -0.01), P-value for trend< 0.05), compared to those in the highest tertile group. The effect estimate attenuated when child's current 25-hydroxyvitamin D level was taken into account [Z-score (95% CI): -0.55 (-1.08, 0.01)]. CONCLUSION AND CLINICAL RELEVANCE: Low levels of 25-hydroxyvitamin D at birth were associated with a higher airway resistance in childhood. Additional adjustment for child's current 25-hydroxyvitamin D level reduced the effect size of the association. Further studies are needed to replicate these findings and to examine mechanisms underlying the observed association and the long-term consequences.

Effects of anesthetic agents on socially transmitted olfactory memories in mice.

Mice can learn a food preference from odor cues transmitted on the breath of a conspecific, even if the "demonstrator" is anesthetized. To our knowledge there are no studies examining the effect of anesthetizing the "observer" on development of memory for socially transmitted food preferences (STFP). In Experiment 1 we found that 2-4 month-old F2 C57Bl/6x129sv male and female mice demonstrated a STFP after a 5min exposure to an anesthetized demonstrator mouse when tested 24h later. In Experiment 2, observer mice anesthetized with Sagatal (60 mg/kg) prior to the "social interaction" preferentially avoided the cued food when tested 24h later. This aversion was not due to any overt aversive effects of this dose of Sagatal because mice that ate the food and were then anesthetized, or could only smell the food for 5 min while anesthetized, showed no preference or aversion. In a third experiment we found that the Sagatal-induced aversion was not a general property of anesthesia because there were varied results produced by observer mice treated with anesthetic drugs with different mechanisms of action. Vetalar (200mg/kg) and Rompun (10 mg/kg) treated animals ate similar amounts of cued and non-cued food at test, indicating an absence of learning. Hypnorm (0.5 ml/kg) treated animals showed a preference for the cued food whereas those treated with Hypnovel (2.5 ml/kg) showed an aversion to the cued food. These results show that the food aversion observed with Sagatal is not a general property of anesthetic agents, but appears to be restricted to those acting primarily on the GABAergic system. Thus, we have shown that under certain conditions it is possible for an anesthetized observer mouse to learn a preference or aversion of a socially-linked olfactory cue.

Prenatal vitamin D deficiency does not exacerbate behavioural impairments associated with prenatal ethanol exposure in juvenile male mice.

There is a high prevalence of vitamin D deficiency and exposure to low levels of ethanol in pregnant women. However, there are a paucity of studies that have addressed the impact of both vitamin D deficiency and ethanol exposure on the offspring's vulnerability to neurodevelopmental disorders later in life. The aim of this study was to examine whether the absence of vitamin D during gestation in mice would alter the effects of prenatal exposure to low dose ethanol on the behaviour and dopaminergic gene expression patterns of juvenile mice. Four-week old female C57BL/6J mice were placed on a prenatal vitamin D deficient (PVD) or standard diet for 6 weeks and mated at 10 weeks of age. Females were exposed to either 10%(v/v) ethanol or water between gestational days 0-8 and all were offered water thereafter. We found that blood ethanol concentration in the dams was not affected by maternal diet. Behavioural analyses of the offspring included ultrasonic vocalizations (USV) at postnatal day (P) 7, locomotion and social interaction at P21. The main findings were increased USV calling rate and impaired social interaction in males with prenatal ethanol exposure (PrEE). Gene expression analysis of transcripts involved in dopamine regulation revealed a main effect of ethanol exposure on dopamine- and cyclic adenosine monophosphate- regulated neuronal phosphoprotein (Darpp-32), a main effect of vitamin D diet on Dopamine 2 Receptors (D2R) and a main effect of Sex on Tyrosine Hydroxylase (TH) expression. The combination of PVD-PrEE did not exacerbate the alterations resulting from PVD or PrEE. Despite the limited evidence to support the interaction of PVD and PrEE during the postnatal period, males were more vulnerable than female offspring to the detrimental effects of PrEE. Therefore, based on these studies in mice we suggest that maintenance of optimal vitamin D levels and abstinence from ethanol during pregnancy would reduce risk of later disruption to brain function and behaviour in the offspring.

No effect of prenatal vitamin D deficiency on autism-relevant behaviours in multiple inbred strains of mice.

Autism Spectrum Disorders (ASD) is a group of neurodevelopmental disorders commonly characterised by verbal and non-verbal communication deficits, impaired social interaction and repetitive, stereotypic behaviours. The aetiology of ASD is most likely a combination of genetic and environmental factors. Epidemiological evidence suggests that prenatal vitamin D deficiency is associated with an increased incidence of ASD. The overall aim of this study was to investigate prenatal vitamin D deficiency on ASD-related behavioural phenotypes in multiple inbred strains of mice. We included two commonly used inbred mouse strains (C57BL/6J and BALB/c) as well as inbred BTBR mice, which show ASD-related behaviours, such as excessive self-grooming, hyperlocomotion, social interaction deficits and altered communication. We also studied the effect of prenatal vitamin D deficiency in a fourth strain; an F1 cross of C57BL/6J x BTBR mice, which have a partial BTBR phenotype. To implement prenatal vitamin D deficiency, female mice were placed on vitamin D deplete diets for ten weeks, including mating and gestation, until littering, when all dams were switched to the control diet. Behavioural symptoms related to ASD were measured, including isolation-induced ultrasonic vocalisations to measure communication, the three-chambered social interaction task to observe social interaction, the open field test to examine hyperlocomotion, assessment of grooming and rearing behaviour and finally the active place avoidance task to observe spatial learning and memory in response to a mild foot shock. Prenatal vitamin D deficiency had a negative impact on preference for social novelty in C57BL/6J mice, despite similar vocalisation phenotypes, and prenatal vitamin D-deficient F1 mice were found to be hypolocomotive in the open field test yet performed better on the active place avoidance task. Despite clear differences between strains, there were no other consistent significant main effects of maternal diet on the behaviour of the offspring. Vitamin D deficiency has been implicated as a risk factor for ASD and these data show that there is greater variation between different inbred strains in ASD-related behaviour, suggesting that prenatal vitamin D deficiency is not sufficient to recapitulate an ASD phenotype in multiple inbred strains of mice.

Content specificity of attentional bias to threat in post-traumatic stress disorder.

BACKGROUND: Attentional bias to affective information and reduced cognitive control may maintain the symptoms of post-traumatic stress disorder (PTSD) and impair cognitive functioning. However, the role of content specificity of affective stimuli (e.g., trauma-related, emotional trauma-unrelated) in the observed attentional bias and cognitive control is less clear, as this has not been tested simultaneously before. Therefore, we examined the content specificity of attentional bias to threat in PTSD. METHODS: PTSD participants (survivors of a multistory factory collapse, n=30) and matched controls (n=30) performed an Eriksen Flanker task. They identified the direction of a centrally presented target arrow, which was flanked by several task-irrelevant distractor arrows pointed to the same (congruent) or opposite direction (incongruent). Additionally, participants were presented with a picture of a face (neutral, emotional) or building (neutral=normal, emotional=collapsed multistory factory) as a task-irrelevant background image. RESULTS: We found that PTSD participants produced overall larger conflict effects and longer reaction times (RT) to emotional than to neutral stimuli relative to their healthy counterparts. Moreover, PTSD, but not healthy participants showed a stimulus specific dissociation in processing emotional stimuli. Emotional faces elicited longer RTs compared to neutral faces, while emotional buildings elicited faster responses, compared to neutral buildings. CONCLUSIONS: PTSD patients show a content-sensitive attentional bias to emotional information and impaired cognitive control.

Vitamin D status during fetal life and childhood kidney outcomes.

BACKGROUND/OBJECTIVES: Maternal vitamin D deficiency during pregnancy may influence offspring kidney health. We aimed to examine the associations of 25-hydroxyvitamin D (25(OH)D) blood levels during fetal life with kidney outcomes at school age. SUBJECTS/METHODS: This study was embedded in a population-based prospective cohort study among 4212 mother-child pairs. We measured maternal second trimester (18-25 weeks) and fetal cord blood (at birth) 25(OH)D levels. At a median age of 6.0 years, we measured children's combined kidney volume, glomerular filtration rate (eGFR) from creatinine and cystatin C serum levels, and microalbuminuria from albumin and creatinine urine levels. RESULTS: Of all mothers, 21.9% had severely deficient levels (25(OH)D <25.0 nmol/l), 25.7% had deficient levels (25.0-49.9 nmol/l), 25% had sufficient levels (50.0-74.9 nmol/l) and 27.4% had optimal levels (⩾75.0 nmol/l). Maternal 25(OH)D levels were not consistently associated with childhood combined kidney volume. Higher maternal 25(OH)D levels were associated with lower childhood eGFR (difference -0.94 ml/min per 1.73 m(2) (95% confidence interval, -1.73; -0.15) per 1 standard deviation (s.d.) increase in 25(OH)D). Maternal 25(OH)D levels were not associated with microalbuminuria. Cord blood 25(OH)D levels were not associated with childhood kidney outcomes. The associations of maternal 25(OH)D levels with childhood eGFR were partly explained by childhood vitamin D status. CONCLUSIONS: Our findings suggest that maternal 25(OH)D levels during pregnancy may influence childhood kidney outcomes. These results should be considered hypothesis generating. Further studies are needed to replicate the observations, to examine the underlying mechanisms and to identify the long-term clinical consequences.

Developmental Vitamin D3 deficiency alters the adult rat brain.

There is growing evidence that Vitamin D(3) (1,25-dihydroxyvitamin D(3)) is involved in brain development. We have recently shown that the brains of newborn rats from Vitamin D(3) deficient dams were larger than controls, had increased cell proliferation, larger lateral ventricles, and reduced cortical thickness. Brains from these animals also had reduced expression of nerve growth factor (NGF) and glial cell line-derived neurotrophic factor. The aim of the current study was to examine if there were any permanent outcomes into adulthood when the offspring of Vitamin D(3) deficient dams were restored to a normal diet. The brains of adult rats were examined at 10 weeks of age after Vitamin D(3) deficiency until birth or weaning. Compared to controls animals that were exposed to transient early Vitamin D(3) deficiency had larger lateral ventricles, reduced NGF protein content, and reduced expression of a number genes involved in neuronal structure, i.e. neurofilament or MAP-2 or neurotransmission, i.e. GABA-A(alpha4). We conclude that transient early life hypovitaminosis D(3) not only disrupts brain development but leads to persistent changes in the adult brain. In light of the high incidence of hypovitaminosis D(3) in women of child-bearing age, the public health implications of these findings warrant attention.

The effect of developmental vitamin D deficiency in male and female Sprague-Dawley rats on decision-making using a rodent gambling task.

Developmental vitamin D (DVD) deficiency is a plausible risk factor for schizophrenia that has been associated with behavioural alterations including disruptions in latent inhibition and response inhibition. The rodent gambling task (rGT) assesses risk-based decision-making, which is a key cognitive deficit observed in schizophrenia patients. The primary aim of this study was to examine risk-based decision-making in DVD-deficient and control rats on the rGT. We also evaluated the performance of female Sprague-Dawley rats on the rGT for the first time. Adult male and female Sprague-Dawley rats from control and vitamin D deficient dams were trained to perform the rGT in standard operant chambers and their performance and choice-preferences were assessed. Female rats were significantly faster to reach rGT training criteria compared with male rats and DVD-deficient rats were faster to reach training criteria than control animals. After reaching stable performance on the rGT DVD-deficient and control rats showed a significant preference for the optimal choice-option in the rGT, but there were no significant effects of sex or diet on these responses. DVD deficiency did not alter the decision-making processes on the rGT because no significant changes in choice-preferences were evident. This is the first study to demonstrate that once established, the performance of females is comparable to male Sprague-Dawley rats on the rGT.

Indomethacin blocks pre-partum nest building behaviour in the pig (Sus scrofa): effects on plasma prostaglandin F metabolite, oxytocin, cortisol and progesterone.

In the pig, nest building occurs in the day preceding parturition (gestation=114--116 days). Nest building behaviour can be induced in pregnant, pseudopregnant and cyclic female pigs following injection of prostaglandin F2alpha. Here we investigated behaviour and endocrine changes after the administration of indomethacin, which inhibits cyclo-oxygenase enzymes and thus prostaglandin synthesis. In experiment 1, pregnant primiparous pigs (gilts) were blood sampled through jugular vein catheters every 20 min from 1000 h on day 113 of pregnancy and behaviour was recorded until birth. Two hours after pre-partum nest building began, animals received 4 mg/kg indomethacin (n=7) or control vehicle (n=8) intramuscularly. Indomethacin-treated animals showed less nest building than controls between 1 and 5 h after injection (P<0.05), during which time they were mostly inactive and lay down for longer than controls. From 5 h before birth until birth there was no significant treatment difference in nest building behaviour. There was a tendency for the start of birth to be delayed in indomethacin-treated animals. Plasma 13,14-dihydro-15-keto-prostaglandin F2 alpha (a major metabolite of prostaglandin F2 alpha) rose during pre-injection nest building and then fell following indomethacin treatment, but was not significantly different between groups when behaviour differed. Plasma oxytocin, cortisol and progesterone were not significantly affected by treatment. In experiment 2, indomethacin-treated non-pregnant gilts (n=7) did not show any changes in activity or posture compared with vehicle-treated controls (n=6) between 90 and 150 min after treatment. These results suggested that indomethacin treatment reversibly and specifically inhibits porcine pre-partum nest building by a mechanism that may involve endogenous prostaglandin F2 alpha synthesis inhibition but is independent of circulating oxytocin, cortisol and progesterone concentrations.

c-fos mRNA expression associated with PGF(2alpha)-induced nest-building behaviour in female pigs.

Domestic pigs, Sus scrofa, build a maternal nest on the day before parturition. A model for nest building has been established in pigs, in which exogenously administered prostaglandin (PG) F(2alpha) may be used to elicit nesting behaviour in cyclic, pseudopregnant and pregnant pigs. The central mechanisms mediating this response are unknown. The present study determined regional brain activity using semi-quantitative analysis of c-fos mRNA, after induction of nest-building behaviour by PGF(2alpha) in Large White pseudopregnant pigs. Oestradiol valerate injections (5 mg/day) were given on days 11-15 of the oestrous cycle to induce pseudopregnancy. The pigs were housed individually in pens (2.8 x 1.7 m) containing straw. On the test day (day 46 or 47 of pseudopregnancy) animals were injected with 3 ml saline (n=5) or 15 mg of PGF(2alpha) (Lutalyse, Upjohn; n=6) intramuscularly. Pigs treated with PGF(2alpha), but not saline, displayed bouts of rooting, pawing and gathering straw, which we interpret as nest building behaviour. The pigs were killed 65 min after treatment, which was 30 min after peak nest building activity, and the brain, uterus and ovaries removed for processing using in situ hybridisation. Saline-treated pigs had elevated levels of c-fos mRNA, compared to background, in the pituitary, corpus luteum and uterus, and a lower, but elevated, level of expression in cerebellum, cortex, hippocampus and olfactory bulb. PGF(2alpha)-treated pigs had significantly higher levels of c-fos mRNA expression than saline-treated pigs in the parvocellular and magnocellular regions of the hypothalamic paraventricular nucleus, the supraoptic nucleus (including the pars dorso-medialis), the neural lobe of the pituitary gland and the cerebellum. PGF(2alpha)-treated pigs also had significantly higher c-fos induction in corpus luteum. These data show that the pattern of c-fos mRNA expression in specific brain areas is different between pigs that show PGF(2alpha)-induced nest building and saline-injected controls.

Prostaglandin F2alpha-induced nest-building behaviour is associated with increased hypothalamic c-fos and c-jun mRNA expression.

Intramuscular injection of the naturally occurring prostaglandin F2alpha (PGF2alpha) to sexually mature female pigs induces luteolysis and rapidly elicits a behavioural response consistent with pre-partum nest-building. Intramuscular injection of the synthetic prostaglandin F2alpha (cloprostenol) also induces luteolysis but no nest-building behaviour is observed. The effects of PGF2alpha, but not cloprostenol, on nest-building behaviour may be mediated via peripheral PGF2alpha receptors (FP) or via direct action on central FP receptors. We have previously shown FP receptor mRNA to be localized in porcine paraventricular nucleus (PVN), supraoptic nucleus (SON) and pars dorso-medialis of the suproptic nucleus (SOD), suprachiasmatic nucleus, choroid plexus and anterior and intermediate pituitary lobes. In this experiment, we examined hypothalamic expression of the immediate early genes c-fos and c-jun mRNA after treatment with PGF2alpha or cloprostenol. Twenty-one 8-month-old nulliparous female pigs (gilts) were injected intramuscularly with a luteolytic dose of PGF2alpha (15 mg), cloprostenol (175 microg) or saline control, their behaviour was recorded and they were killed 60 min later. Coronal hypothalamic sections and control ovarian tissues were incubated with 45-mer oligonucleotide probes complementary to porcine c-fos and c-jun genes using standard in situ hybridization histochemistry techniques. Significantly higher c-fos and c-jun mRNA expression was found in PGF2alpha-treated compared to saline or cloprostenol-treated pigs in the PVN, SON and SOD. Significantly higher c-fos and c-jun mRNA expression was found in corpus lutea of PGF2alphaand cloprostenol-treated pigs compared to saline controls. Treatment with PGF2alpha induced nest-building behaviour whereas treatment with cloprostenol and saline did not. This suggests that PGF2alpha, or one of its metabolites, and not cloprostenol, crosses the blood-brain barrier and acts directly on hypothalamic receptors to mediate its effect on nest-building behaviour.

Light exposure of the embryo and development of behavioural lateralisation in chicks, I: olfactory responses.

Chicks exposed to light during late foetal life experience stimulation of the right eye only and, in consequence, develop asymmetries of the crossed visual projections from thalamus to forebrain and differences in performance of some visual tasks when using the right or left eye. The present study compared dark- and light-incubated chicks in a test of olfaction in which clove oil odour was presented together with a coloured bead. When the chicks were tested with a blue bead and using the right nostril (left nostril occluded by wax), head shaking and pecking were elevated, compared to pretest responses to an unscented, white bead. No significant elevation of head shaking occurred in chicks tested with the blue bead and using the left nostril, although pecking increased, which indicates that these chicks attended to the visual parameters of the bead but not the odour. It appears that, when the left nostril is used, attention to an attractive visual stimulus suppresses responses to olfactory input to the left hemisphere. When the clove oil odour was presented together with a less attractive, red bead, no significant lateralisation emerged. Light or dark experience prior to hatching had no effect on the lateralised performance of the blue-bead test.

Responses to odorants by the domestic chick.

We have developed a method to measure responses to graded concentrations of volatile chemicals by domestic chicks (Gallus gallus domesticus). Concentration-response curves were obtained, from which 50% effective concentration (EC50) values were determined. One-day-old chicks were presented with a 4-mm diameter colored bead, at which they pecked readily, affixed to a tube containing log dilutions of odorant. The chick was exposed to the odorant when it pecked at the bead. Various methods of presentation were tried. The method preferred minimized the number of chicks required by allowing repeated testing. Habituation to visual cues was prevented by changing the color of the bead on each presentation. The number of pecks directed at the bead and the amount of head shaking that occurred while the chick was exposed to the stimulus during the 10-s trial were scored from video recordings. Chicks demonstrated increased amounts of head shaking with increasing concentrations of isoamyl acetate or allyl sulfide; low concentrations stimulated pecking and higher concentrations suppressed it. Coincident EC50 values for pecking and head shaking (approximately 1% for isoamyl acetate and allyl sulfide) indicate that they may be controlled by the same mechanism, albeit inversely. There was no relationship between the amount of pecking and the concentration of eugenol, but the EC50 value for head shaking was at the 30% concentration. The results demonstrate that one-day-old chicks show graded responses to graded concentrations of odors and that they demonstrate differential sensitivity to different odorants. Possible involvement of the trigeminal system in these responses is considered.

Relative importance of odour and taste in the one-trial passive avoidance learning bead task.

The relative importance of taste and odour cues in a one-trial passive avoidance learning (PAL) task was examined. One-day-old chicks were presented with a small bead and different combinations of the taste and odour of methyl anthranilate (MeA). The chicks had received three consecutive pretraining trials where they were presented with white, red, and blue beads. They were then trained with a red bead presented in one of four possible conditions: dry and unscented, with the odour but not the taste of MeA, with the bitter taste but not the odour of MeA (the chicks' nostrils were occluded with a wax preparation), or with the taste and odour of MeA. Recall was tested 10 min after training by presenting a red and then a blue bead with no odour or taste added. The number of pecks made at the bead and the number of bouts of head shaking during each of the trials were scored. During testing, chicks that were trained with the odour of MeA alone pecked less at a red bead than at a blue bead, compared with chicks trained with a dry and unscented bead, indicating that they discriminated between the training bead and a bead of a different colour. There was no significant difference between the discrimination ratio of chicks trained with the odour, taste, or taste and odour of MeA. These results demonstrate that chicks can perform PAL using taste and/or odour cues.

Effects of ovariohysterectomy on prostaglandin F2alpha-induced nesting behaviour in pigs.

Exogenously administered prostaglandin (PG) F2alpha induces behaviour similar to prepartum nest building in pregnant, pseudopregnant and nonpregnant female postpubescent pigs (Sus scrofa). These effects may be regulated by PGF2alpha-induced endocrine changes within the reproductive tract, such as those that initiate luteolysis. This study investigated the short-term effects of ovariohysterectomy on PGF2alpha-induced nesting behaviour in nonpregnant females. Cyclic 9-month-old virgin female pigs (gilts) received an oral dose (20 mg/day) of a synthetic progestogen (altrenogest; Regumate porcine, Hoechst, Milton Keynes, UK) for 18-21 days to synchronize oestrus. The gilts were then ovariohysterectomized (n=8) or sham-operated (n=7) on Days 3-8 after oestrus. They were housed individually and initially subjected to a series of control behavioural tests to establish the effect of ovariohysterectomy on their responses to the experimenters, novel objects, straw bedding and space restriction. Ovariohysterectomized gilts had a shorter latency to approach the experimenters than sham-operated animals, but there were no differences in their responses to a novel object, straw bedding or space restriction. Twelve to 16 days after oestrus, corresponding to the midluteal phase in sham-operated gilts, they were treated intramuscularly with 15 mg PGF2alpha (0.12 mg/kg, dinoprost; Lutalyse, Upjohn, Crawley, UK). PGF2alpha treatment induced a significant increase in straw gathering in ovariohysterectomized but not in sham-operated gilts. Other nesting behaviours, including rooting and pawing at straw, were induced in all animals. These results show that the uterus and ovaries are not required for the expression of PGF2alpha-induced nesting behaviour and the removal of the reproductive tract appears to have facilitated increased levels of gathering. This suggests that PGF2alpha induces luteolysis and nest building separately, and that PGF2alpha or a metabolite, may act centrally to mediate directly its effects on prepartum nest building in the pig.

Behavioral responses to intramuscular injections of prostaglandin F(2 alpha) in female pigs.

This study investigated the effect of different doses (0-1.25 mg/kg IM) of prostaglandin (PG) F(2 alpha) on the behavior of female pigs (Sus scrofa). Six-month-old cyclic nulliparous sows (gilts) were housed and tested individually in strawed pens (2.8 x 1.7 m). All doses of PGF(2)alpha induced rooting, pawing at the ground, and gathering straw. In the hour following treatment the frequency of pawing increased with increasing dose to reach a maximum level with the highest dose given. The frequency to gather straw was highest in pigs treated with the lowest dose (0.008 mg/kg). The frequency of oronasal contact with the floor and pen walls was unaffected by dose. Scratching, locomotion, and changes in body posture were highest following treatment with the three highest doses of PGF(2 alpha). Many of the behaviors observed following PGF(2 alpha) treatment are characteristic of prepartum nesting behavior in pregnant sows. We conclude that two key components of maternal nest-building behavior, pawing, and gathering straw, are affected differentially by different doses of PGF(2 alpha). The implications of these results on the mechanisms underlying maternal nest building in pigs are discussed.

Effects of oestrogen supplementation and space restriction on PGF2alpha-induced nest-building in pseudopregnant gilts.

This study examined the role of oestrogen supplementation on PGF2alpha-induced nest-building in pseudopregnant gilts. Oestradiol valerate (5 mg/day) injections were given on Days 11-15 of the oestrous cycle to induce pseudopregnancy. A further series of injections of either oestradiol valerate (5 mg/day) or vehicle were given on days 44-46 of pseudopregnancy to reflect more closely the hormone profile seen in pregnancy. Nest-building was induced by a single intramuscular injection of 15 mg of PGF2alpha (Lutalyse) on Day 47 of pseudopregnancy. The gilts were housed in pens (2.8 x 1.7 m) containing straw in experiment 1 or chronically confined in crates (0.6 x 1.7 m) that did not contain straw on days 44-48 of pseudopregnancy for experiment 2. Oestrogen supplemented gilts had significantly higher concentrations of circulating 17beta-oestradiol on day 47 of pseudopregnancy but there were no significant differences between treatments for circulating levels of prolactin, progesterone, cortisol or oxytocin, or for any behavioural measure in either experiment. These results indicate that there is no direct effect of supplementing already pseudopregnant gilts with oestradiol valerate on PGF2alpha-induced nest-building. The results also show that the pre-partum environment has a pronounced effect on nest-building behaviours and that non-pregnant pigs might be a useful model for pre-partum nest-building in this species.

Influence of environmental temperature on PGF(2alpha)-induced nest building in female pigs.

Domestic pigs build a maternal nest in the day preceding parturition. We have shown that prostaglandin F(2alpha) (PGF(2alpha)) induces nest building behaviour in non-pregnant pigs. The aim of this experiment was to examine the effects of different environmental temperatures on PGF(2alpha)-induced nest building. Data were collected from 9 Large White (LW) and 10 Large Black (LB) 8-9-month-old nulliparous sows (gilts). The pigs were housed in social groups between experiments and tested individually in pens (1.8mx1.8m) containing straw, within an environmentally controlled chamber. Pigs were habituated to the testing pens (maintained at 17 degrees C) and tested once at each of three temperatures (low, 5 degrees C; moderate, 17 degrees C; high, 30 degrees C). During testing the temperature of the chamber was adjusted at 09.00h and had reached set point by10.00h. The pigs were injected intramuscularly with 3ml saline at 10.30h and 0.1mg/kg PGF(2alpha) (Lutalyse, Upjohn) at 11.30h. Behaviour was scored for 1h after treatment with saline and 1h after treatment with PGF(2alpha) using one/zero sampling from video recordings. Nest building behaviour (rooting, pawing and gathering straw) was induced by PGF(2alpha) at all temperatures in both LW and LB breeds. There was a significant increase in rooting behaviours with decreasing temperature. No significant effects of temperature were found on the scores for gather or paw. The pigs spent more time lying down at the high compared to the low temperature after both saline and PGF(2alpha) treatment. Other behaviours unrelated to nest building but induced by PGF(2alpha), such as scratching, were unaffected by temperature. The results show that the nest building behaviour of non-pregnant pigs can be induced by exogenous PGF(2alpha) treatment, and that some, but not all, aspects of PGF(2alpha)-induced nest building (rooting but not pawing or gathering) are altered by environmental temperature.

PGF(2alpha)-induced nest building and choice behaviour in female domestic pigs.

The domestic pig, Sus scrofa, builds a maternal nest in the day before parturition. A model for porcine nest building has been established, in which exogenously administered prostaglandin (PG)F(2alpha) is used to induce nesting behaviour in cyclic, pseudopregnant and pregnant pigs. This experiment was designed to examine the effect of PGF(2alpha) on the preferences of non-pregnant gilts for pens bedded with straw compared with bare pens. Ten 6-month-old nulliparous female pigs (gilts) were tested in an arena, which consisted of four pens (1.8mx1.7m), a neutral area (1.5mx3.4m) and a start area (1.5mx3.4m). Two of the pens contained 2kg of fresh straw and the remainder of the testing arena was devoid of straw. On the first day of testing half of the pigs were given a control intramuscular injection of 3ml 0.9% saline and the remainder were given an intramuscular injection of 15mg PGF(2alpha) and their behaviour scored for 1h after treatment. On the following day the treatments were reversed, such that each pig was given both treatments (saline or PGF(2alpha)). There was no significant effect of the order of treatment on behaviour. After saline-treatment the pigs spent most of their time in the pens containing straw (59%) and the least amount of time in bare pens (5%). In the straw pens, saline-treatment induced bouts of oronasal contact with straw of a relatively long duration (11-100s), which we interpret as foraging. In the hour after PGF(2alpha)-treatment the pigs also spent most of their time in the pens containing straw (44%) and the least amount of time in bare pens (10%), but they interacted with the straw in a markedly different way. PGF(2alpha)-treated pigs displayed bouts of oronasal contact with straw of a relatively short duration (2-10s) which, together with high frequencies of pawing at straw, lifting and carrying straw in the mouth, we interpret as nest building behaviour. Superimposed on this is the finding that gilts spend more time in the neutral areas after PGF(2alpha)-treatment than they did after saline-treatment. PGF(2alpha)-treated pigs spent most of their time engaged in nesting behaviour within the straw pens but they also gathered and deposited straw in different areas of the test arena (neutral and start areas); behaviours not seen after saline-treatment. We conclude that pigs generally prefer a pen containing straw bedding to a bare pen but that PGF(2alpha) alters the way they interact with straw, inducing behaviour similar to prepartum nest building.