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PubMed2005

Expression of growth hormone receptor 1A mRNA is decreased in dairy cows but not in beef cows at parturition.

The promoter controlling expression of a major bovine growth hormone (GH) receptor (GHR) mRNA variant, GHR 1A, contains a common DNA element for transcription factors hepatocyte nuclear factor 4alpha (HNF-4alpha), hepatocyte nuclear factor 4gamma (HNF-4gamma), and chicken ovalbumin transcription factor II (COUP-TFII). Expression of GHR 1A mRNA is decreased in the liver of dairy cows at parturition. The objective of this study was to determine whether reduced expression of GHR 1A mRNA in dairy cows at parturition is associated with changed expression of HNF-4alpha, HNF-4gamma, or COUP-TFII mRNA. Liver biopsy samples were taken from multiparous Holstein cows 7 to 23 d before parturition, within 24 h after parturition (i.e., at parturition), and 8 to 18 d after parturition, and the relative amounts of GHR 1A, insulin-like growth factor-I (IGF-I), HNF-4alpha, HNF-4gamma, and COUP-TFII mRNA in these samples were measured by ribonuclease protection assays. As expected, expression of GHR 1A, total GHR, and IGF-I mRNA was decreased at parturition, compared with that detected prepartum or during the postpartum period. Expression of HNF-4alpha and COUP-TFII mRNA was unchanged, but that of HNF-4gamma mRNA was increased at parturition. The same study was also conducted in multiparous Angus cows 7 to 23 d before parturition, at parturition, and 8 to 18 d after parturition. Neither expression of GHR 1A, total GHR, or IGF-I mRNA, nor expression of HNF-4alpha, COUP-TFII, or HNF-4gamma mRNA was changed in the liver of beef cows at parturition. These results together suggest that, at the molecular level, decreased expression of GHR 1A mRNA in the liver of dairy cows at parturition may involve increased expression of HNF-4gamma mRNA and that, at the systemic level, decreased expression of GHR 1A mRNA is not a direct result of the end of pregnancy, parturition, or the initiation of lactation.

Animals↗
PubMed1996

Oxytocin released within the supraoptic nucleus of the rat brain by positive feedback action is involved in parturition-related events.

Oxytocin is released within the supraoptic nucleus during parturition and suckling. During suckling, such release is important in positive feedback stimulation of oxytocin neurons. We have investigated whether oxytocin released within this hypothalamic nucleus during parturition (1) acts on local receptors to further amplify its own release in a positive feedback manner and (2) is critically involved in the regulation of the delivery process. To examine the effect of the oxytocin antagonist on oxytocin release within the supraoptic nucleus, microdialysates were sampled before and during parturition and either vehicle or the antagonist was infused adjacent to the microdialysis probe directly into the supraoptic nucleus after delivery of the second pup. Intranuclear infusion of an oxytocin receptor antagonist (des-Gly-NH2d(CH2)5[Tyr(Me)2Thr4]OVT; 50 ng/0.5 microliters) significantly (P < 0.01) diminished the parturition-related rise in oxytocin release within the supraoptic nucleus and reduced the number of pups delivered during the first and second 30-min dialysis period compared to vehicle-treated controls. Bilateral infusion of the oxytocin receptor antagonist into the supraoptic nucleus after delivery of the second pup significantly slowed parturition (P < 0.05), although the parturition-related rise in plasma oxytocin concentration was unchanged. In addition, the onset of suckling was significantly affected by the antagonist as indicated by fewer liver pups and fewer surviving pups with milk in their stomachs 24 hours after parturition (P < 0.05). To seek other, periventricular sites of oxytocin action during parturition, oxytocin or the oxytocin antagonist was infused into the lateral cerebral ventricle from the birth of pup 2. Via this route, oxytocin speeded up parturition, but the antagonist was ineffective; thus it appears that periventricular oxytocin-sensitive sites are not normally active in promoting parturition, and can do so. The findings indicate a receptor-mediated positive feedback action of oxytocin on its own release within the supraoptic nucleus during parturition, which seems to be involved in the progress of parturition without significantly affecting circulation oxytocin levels. Oxytocin released within the supraoptic nucleus might be important for the coordinated activation of oxytocin neurons and for the synergistic central and peripheral oxytocin effects involved in the regulation of parturition-related events necessary for the survival of the newborn, including the onset of lactation.

Animals↗
PubMed2002

Hormonal measurements in late pregnancy and parturition in dairy cows--possible tools to monitor foetal well being.

Three dairy heifers (A, B and C) were induced to parturition with two prostaglandin (PG) F(2alpha) injections on day 268 and 269 of pregnancy. Signs of approaching parturition were carefully observed. The following parameters were registered: degrees of calving difficulty, date and time of parturition, calf's birth weight and calf's sex. Body temperature was measured and blood samples were taken every 3 h 3 days before the first PGF(2alpha) injection until 3 days after parturition. The plasma concentrations of the PGF(2alpha) metabolite, progesterone, cortisol, oestrone sulphate and pregnancy associated glycoproteins (PAGs) were analysed. Heifers A, B and C delivered 48, 51 and 57 h after the first PGF(2alpha) injection, respectively. Heifer A delivered without any signs of calving difficulty, whereas, the parturition was considered to be slight and moderate difficulty occurred in the delivery of heifers B and C, respectively. The calf of heifer C, without any abnormal gross-evidences, was stillborn. All animals had retained foetal membranes. A slight increase of the PGF(2alpha) metabolite at the time of parturition was found only in heifer C, whereas the levels dramatically increased in all animals 15-24 h after parturition. At the same time, progesterone levels decreased within 3 h after the first PGF(2alpha) injection (P < 0.05) and reached 0.8, 2.7 and 12.4 nmol/l at the time of parturition in heifers A, B and C, respectively. High release of cortisol at the time of parturition was seen in heifer C. Rising levels of oestrone sulphate around the time of parturition were recorded in all heifers, whereas, increasing levels of PAGs were recorded only in heifer A. In conclusion, the patterns of the PGF(2alpha) metabolite, cortisol, progesterone and PAGs were changed in the cases of calving difficulty and stillbirth after PGF(2alpha)-induction of parturition. However, the relationship between oestrone sulphate and PAGs and the status of foetal well being prior to parturition require further elucidation.

Animals↗
PubMed1985

Control of time of parturition in pigs.

Injection of prostaglandin (PG) F-2 alpha or its analogues has provided a technique to induce parturition after Day 110 of gestation in the sow. The mean interval from PG injection to parturition ranges from 24 to 28 h, but only 50-60% of the sows farrow during an 8-10 h working day, and as many as 20% of sows may begin parturition before the injection of PG or less than 22 h after the injection. The duration of parturition is positively associated with the incidence of stillbirths and perinatal death so that techniques to reduce the duration of parturition may save piglets. Early parturition has been prevented by feeding sows progestagens, PG synthesis inhibitors and hypothalamic function inhibitors. These compounds were detrimental to piglet survival if they delayed parturition too long after the expected time of parturition. Parturition was delayed in sows up to 1.5 days by altrenogest, 1.6 days by meclofenamic acid, 2.7 days by indomethacin, and 3 days by methallibure without increased incidence of stillborn piglets compared with control sows. Injection of PG after administration of altrenogest or meclofenamic acid was successful in experiments with sows; parturition could be confined to a 5-day working week with no increase in stillborn piglets compared with control sows. Relaxin injected at 48 and 24 h before or only 24 h before injection of PG increased the proportion of sows farrowing 22-32 h after PG to 86.2% compared with sows injected only with PG (53.3%, P less than 0.01). Oxytocin injected 20 h after injection of PG increased the proportion of sows farrowing 20-28 h after PG to 90.4% compared with sows injected only with PG (49.2%, P less than 0.005). Injection of 25-60 i.u. ACTH on Day 110 of gestation did not shorten the length of gestation, but did decrease the incidence of still born piglets by 0.2 piglets/litter (P less than 0.05). An injection of the beta-adrenergic antagonist, carazolol, during labour before the birth of the first piglet decreased the duration of parturition and the incidence of stillborn piglets particularly in primiparous sows (P less than 0.05). Carazolol injected with oxytocin 20 h after injection of PG decreased the interval from PG to parturition by 2 h compared with sows injected with only PG and oxytocin.(ABSTRACT TRUNCATED AT 400 WORDS)

Adrenergic beta-Antagonists↗
PubMed2001

15-ketodihydro-PGF2 alpha, progesterone and cortisol profiles in heifers after induction of parturition by injection of dexamethasone.

In order to study rapid changes in 15-ketodihydro-PGF2 alpha, cortisol and progesterone in the period preceding parturition in cattle, pre-term parturition was induced in 4 late pregnant heifers. Parturitions were induced by 2 intramuscular injections of 20 mg dexamethasone with a 24-h interval. The first injection was made on days 254, 258, 264 and 265 in gestation, respectively. Twenty-four h before the first injection an intravenous polyurethane cannula was inserted. Blood samples were collected at least every hour until 12 h after parturition and during the second stage of labour at least 6 times per hour. Plasma was analysed for 15-ketodihydro-PGF2 alpha and progesterone by radioimmunoassays, and for cortisol by an ELISA. The average time from injection to parturition was 7.7 (6.6-8.9) days (mean (range)). Two of the heifers had retained foetal membranes (RFM). At the start of the experiment the levels of PGF2 alpha metabolite were low (< 300 pmol/L) and increased slowly to levels between 1000 and 2000 pmol/L at one day before parturition. During the last day, however, the levels increased rapidly and the highest levels (> 10,000 pmol/L) were reached at the time of delivery. No pulsatile release was seen. Immediately after foetal expulsion the PG-metabolite levels decreased rapidly in all animals. In the 2 animals with RFM, however, this decline ceased within a few h. The PG-metabolite levels in these animals then started to increase and reached levels as high as during parturition. Luteolysis occurred between 1.6 and 0.4 days before parturition in all animals. The cortisol profile showed a distinct peak at the time of parturition in the RFM heifers. This peak was absent in the non-RFM heifers. This study shows that the PGF2 alpha release at prepartal luteolysis and parturition is not pulsatile in cattle and that cortisol profiles in heifers with retained foetal membranes might differ from the profiles in non-RFM heifers at the time of parturition.

Animals↗
PubMed2002

Induction of parturition in snow skinks: can low temperatures inhibit the actions of AVT?

The influence of environmental factors on the timing of parturition has not been investigated in viviparous squamates. We investigated the interaction between temperature and parturition in two viviparous skink species, the southern snow skink (Niveoscincus microlepidotus) and the metallic skink (N. metallicus). In these species, the timing of parturition is separated from the completion of embryonic development; the delay is attributed to their cool and variable habitats. We examined whether the neurohypophyseal hormone arginine vasotocin (AVT) stimulated parturition in southern snow skinks with late stage embryos in autumn (approximately 6-7 months prior to parturition) and in metallic skinks with late stage embryos in summer (approximately 2-3 weeks prior to parturition). The experiments were conducted at a range of environmentally relevant temperatures (6 degrees C, 15 degrees C, 22 degrees C, and 28 degrees C). AVT induced parturition in both species at all temperatures; time until birth, however, occurred more quickly at warmer temperatures (22 degrees and 28 degrees C), whereas cooler temperatures delayed parturition. We hypothesize that if cool temperatures are preventing parturition, then temperature must act at some level within the brain to prevent or slow the secretion of AVT. Future experiments will need to determine how temperature influences AVT production. Further research is also required to determine how the timing of parturition is influenced by interactions between temperature, photoperiod, and seasonal hormone patterns.

Animals↗
PubMed2000

Uterine expression of prostaglandin H2 synthase in late pregnancy and during parturition in prostaglandin F receptor-deficient mice.

PG production in uterine tissues is important for many physiological processes in late pregnancy, including parturition. We examined the expression of the PGH2 synthases, cyclooxygenase-1 (COX-1) and COX-2, in uterine tissues during late pregnancy, using PGF receptor-deficient (FP-/-) mice. Female FP-/- mice are unable to deliver normal fetuses at term, as they do not undergo luteolysis necessary for parturition. In wild-type mice, COX-1 messenger RNA (mRNA) was expressed in the endometrial epithelium, myometrium, and decidua throughout late pregnancy. The expression of COX-1 mRNA in the endometrial epithelium and myometrium decreased both in wild-type mice undergoing natural parturition and in FP-/- mice undergoing ovariectomy-induced parturition, but expression of COX-1 mRNA was enhanced in FP-/- mice at the expected term. In wild-type mice, COX-2 mRNA was not expressed in the myometrium before parturition, but was markedly induced during parturition. This induction of COX-2 was absent in FP-/- mice at the expected term, but was found during ovariectomy-induced parturition in these mice. Expression of COX-2 proteins was confirmed by immunohistochemical analysis. Thus, in uterine tissues, myometrial expression of COX-2 is closely associated with the occurrence of parturition, but uterine expression of COX-1 is induced much earlier and kept at a high level until parturition occurs. These results suggest that COX-1-derived PGs are responsible for the induction of luteolysis, and that COX-2-derived PGs play a role in the final pathway of parturition.

Animals↗
PubMed2001

Establishment of the prediction table of parturition day with ultrasonography in small pet dogs.

To establish a prediction table of parturition day the real-time B-mode ultrasonographic examinations were performed in the 8 pregnant Malteses and 10 Yorkshire terriers (total pups, 25 and 38 pups, respectively) from 18 days of gestation until the parturition. Ovulation was designated the first day of gestation (day 0). Extra fetal and fetal structures were measured from all conceptues. The parameters that exhibited the best correlation to parturition were used to compile a prediction table of parturition day. To testify the precision of the prediction table of parturition day, the 15 pregnant Malteses (48 pups) and 13 pregnant Yorkshire terriers (42 pups) with unknown mating time were examined using ultrasonography. Inner chorionic cavity diameter on days 18 to 37 and fetal head diameter on day 38 to parturition that showed the best correlation to gestational age were the most pertinent to the estimation of gestational age and the prediction of parturition day. The two parameters were used to compile a prediction table of parturition with averaged regression equations. In verificational examinations, with the exception of I Yorkshire terrier (3.6%) having 1 fetus, 18 of 28 bitches (64.3%) delivered exactly on the date predicted and 9 of 28 bitches (32.1%) delivered within I day of the date predicted. Therefore, the prediction table of parturition day seems to be a useful tool of the prediction of parturition day in practice.

Animals↗
PubMed2005

Induction of parturition in the bitch with the progesterone-receptor blocker aglépristone.

The triggering mechanism for parturition in the bitch remains unclear. Consequently, the development of drugs to successfully induce parturition in the dog has been difficult. The aim of this study was to evaluate the efficacy of the progesterone-receptor blocker aglépristone for the induction of parturition in beagle bitches. The course of parturition was therefore investigated in six parturitions induced by aglépristone and in six spontaneous parturitions. In addition, data were collected on pup survival and growth rates. Aglépristone was administered twice with a 9h interval on day 58 of pregnancy. If parturition did not proceed a standard intervention protocol was applied. Expulsion of the first pup occurred between 32 and 56 h after the first treatment with aglépristone, at which time the plasma progesterone concentration was still elevated. Accordingly, the gestation length of the bitches in the induced group (59.5+/-0.2 days) was significantly shorter than that of the spontaneously whelping bitches (62.2+/-0.5 days). The expulsion phase length, the inter-pup interval, the number of puppies born dead, and the number of clinical interventions needed during parturition did not significantly differ between the spontaneously whelping and the induced group. Pup survival and mean birth weights in the two groups did not differ significantly and aglépristone treatment had no significant influence on the growth rates. The results of this study show that aglépristone is an effective drug which can be used safely for the induction of parturition in the dog.

Animals↗
PubMed1992

Oxytocin, amino acid and monoamine release in the region of the medial preoptic area and bed nucleus of the stria terminalis of the sheep during parturition and suckling.

Microdialysis sampling was used to measure the release of oxytocin (OXY) and monoamine and amino acid transmitters from the region of the medial preoptic area (MPOA) and the bed nucleus of the stria terminalis (BNST) during parturition and suckling in sheep. Results showed that OXY and gamma-aminobutyric acid release increased in both the MPOA and BNST during parturition and suckling. Noradrenaline (NA) release increased in both structures during parturition but not during suckling. Dopamine (DA) release increased in the MPOA and decreased in the BNST during both parturition and suckling. Aspartate release increased in the MPOA during parturition, and the BNST during suckling, and glutamate release increased in the MPOA and BNST at parturition and only in the BNST during suckling. No changes in the release of serotonin or taurine occurred in these structures during parturition or suckling. In a further experiment on 6 estrogen-primed sheep, OXY (10 micrograms/ml) was infused into the MPOA via bilaterally placed microdialysis probes. This treatment inhibited rejection behavior towards lambs, but did not activate positive maternal responses. These OXY infusions also stimulated release of NA. These results show that complex patterns of neurochemical release occur in two closely related areas of the brain, the BNST and MPOA, during parturition when maternal behavior is stimulated. However, while these patterns of release are similar in the two structures, particularly at birth when maternal behavior is stimulated, they are not identical during labor contractions and suckling. The release of oxytocin within the MPOA during parturition may be important for stimulating a reduction in aggression towards lambs, although this action might be mediated via the effect of OXY on NA release.

Amino Acids↗
PubMed1994

Follicular and FSH responses to parturition during the anovulatory season in mares.

The ovaries of periparturient pony mares (n=9 to 16 parturitions per month for January to April) were scanned ultrasonically on the day of parturition, while those of postpartum and control mares (n=12) were examined at least twice weekly. Four mares had apparent lactational anovulation (incidence, 7%) that corrected spontaneously (1 mare) or within 14 d after the weaning of foals on August 10 (3 mares). All but 2 of the postpartum ovulations occurred after April 29; that is, parturition did not effectively stimulate ovulation in ponies foaling during the anovulatory season. Mean diameter of the largest follicle per month increased (P<0.001) progressively in the controls (means: 11.4, 14.4, 19.0 and 24.5 mm for January to April, respectively). In the parturient mares, the diameter of the largest follicle on day of parturition did not increase over months (range of means: 13.6 to 16.9 mm), indicating that a suppressive effect of pregnancy counteracted the stimulatory effect of season. Within each month of parturition, diameter of the largest follicle increased (P<0.05) between Day 0 (day of parturition) and Day 3 or 7. Blood samples for FSH assay were taken daily for 14 d from 6 mares with parturition in the middle of each month and from 6 controls on the corresponding calendar days. In periparturient mares, a significant increase in mean FSH concentrations occurred for all months of parturition between Day-2 and Day 0, followed by a significant decrease between Day 3 and Day 7. Maximum means for the periparturient FSH profile were temporally related to the beginning of follicular growth. In the controls, FSH concentrations were not affected by month or day, or by their interaction. Within each month, mean FSH concentrations were lower (P<0.05) in the periparturient mares than in the controls (averaged over all months: 3.9+/-0.1 versus 7.9+/-0.3 ng/ml) even though follicular growth was greater following parturition than during the corresponding calendar days in controls.

Journal Article↗
PubMed1998

Length of postpartum anestrus in goats in subtropical Mexico: effect of season of parturition and duration of nursing.

The aim of this study was to determine whether season of birth and length of nursing affected the duration of postpartum anestrus in Creole female goats maintained on a constant plane of nutrition in subtropical Mexico. Three experiments were conducted in the Laguna region in the State of Coahuila, Mexico (26 degrees N). In the first experiment, 34 goats gave birth in January; in the second, 31 females gave birth in May; and in the third, 22 goats kidded in October. At parturition, females were allocated to 1 of 3 groups based on body weight and date of parturition: kids were weaned at 2, 30 or 90 d according to their group. After weaning, females were milked manually once a day until the end of the study. All animals were kept in a shed and were fed alfalfa ad libitum and given 200 g of concentrate daily. Starting 1 wk after parturition, estrous behavior was detected twice daily using an apron-bearing male, and blood samples were obtained twice weekly to determine ovarian activity from the plasma progesterone levels. A strong effect of month of parturition was found on the duration of postpartum anestrus (P < 0.0001), which was longer in females kidding in January (about 200 d) than in those kidding in May (about 100 d) or October (about 50 d). A tendency for an interaction between season of parturition and length of nursing was observed in the length of anovulation (P < 0.07): for parturition in October, anestrus was longer when kids were weaned after 90 d than after 2 or 30 d (P < 0.01). Season of parturition also affected dates of reinitiation of ovulatory and estrous activity (P < 0.001). Proportions of normal, short and long cycles and of associations between estrous and ovulations were not influenced by season of parturition or the age of weaning. These data demonstrate that in subtropical latitudes, season of parturition can dramatically influence the duration of postpartum anestrus independently of the availability of food.

Anestrus↗
PubMed1998

Plasma concentrations of 15-ketodihydro-PGF2 alpha, progesterone, oestrone sulphate, oestradiol-17 beta and cortisol during late gestation, parturition and the early post partum period in llamas and alpacas.

Plasma concentrations of 15-ketodihydroprostaglandin (PG) F2 alpha, progesterone, oestrone sulphate, oestradiol-17 beta and cortisol during late gestation, parturition and the early post-partum period were measured in six llamas and five alpacas. During the last 100 days of pregnancy, 15-ketodihydro-PGF2 alpha concentrations increased steadily until the day of parturition when a massive release was detected (P < 0.01) concomitant with a decrease in progesterone concentrations (P < 0.01). The highest PGF2 alpha metabolite concentrations (159 +/- 35 nmol l-1 and 92 +/- 29 nmol l-1 in llamas and alpacas respectively) were detected in the sample collected during the morning on the day of parturition. Basal concentrations were registered by day 3 after delivery. Plasma concentrations of oestrone sulphate started to increase 80 days before parturition and reached peak concentrations immediately before parturition (15 +/- 3 nmol l-1 in llamas and 18 +/- 5 nmol l-1 in alpacas). Oestrone sulphate concentrations dropped sharply (P < 0.01) on the day of parturition in llamas and one day later in alpacas, whereupon they remained relatively unchanged until at least 20 days postpartum. Oestradiol-17 beta concentrations were higher than 180 pmol l-1 during the last 45 days of pregnancy, began to decrease on the day of parturition and reached very low concentrations within the following two days. High oestradiol-17 beta concentrations were registered 7 days postpartum in all alpacas (P < 0.05) and within 10 days of parturition in five of six llamas (P < 0.01). No significant cortisol peaks were observed around parturition, but mean concentrations were increased in both species.

Animals↗
PubMed1997

Profile of monoamine and excitatory amino acid release in rat supraoptic nucleus over parturition.

The magnocellular oxytocin neurons of the hypothalamic supraoptic (SON) and paraventricular nuclei play an important role in the initiation and maintenance of parturition in the rat. As little is known about the neural inputs responsible for activating oxytocin neuron activity at this time, we used the technique of microdialysis to examine the profile of monoamine and excitatory amino acid neurotransmitter release within the SON before and during parturition. Microdialysis probes were implanted into the SON of anesthetized pregnant rats (n = 8) on the morning of the day preceding parturition (day 20), and 15-min dialysate samples were collected from freely moving animals over the following 2 days until 3 h after birth of the last pup. On the day of parturition (day 21), dialysate concentrations of norepinephrine were significantly increased (P < 0.05) in the hour leading up to the expulsion of the first pup and, compared with those on the previous day, remained at significantly (P < 0.05) elevated levels throughout the course of parturition. A significant (P < 0.01) increase in glutamate concentrations was also detected, although in this case, it was only elevated transiently in the 15-min period immediately before the onset of pup expulsion. Mean levels of dopamine were not different between days 20 and 21, but a significant increase in dopamine release was detected specifically during the second half of parturition. No significant changes in serotonin and aspartate concentrations were observed on days 20 and 21 or in relation to parturition. This study provides an analysis of neurotransmitter release in the SON over parturition and indicates that norepinephrine concentrations are elevated well in advance of the onset of pup expulsion, whereas a burst of glutamate release occurs immediately before the birth of the first pup. Such changes are likely to reflect activity in afferent inputs to the SON and may represent neurochemical events involved in the initiation and maintenance of parturition.

Animals↗
PubMed1989

Interruption of parturition in rats by morphine: a result of inhibition of oxytocin secretion.

Oxytocin secretion is inhibited by opioids, and oxytocin is important in parturition. The effects on parturition of morphine, a relatively selective mu-opioid receptor agonist, were studied in the rat. Morphine or vehicle with or without the opiate antagonist naloxone were administered immediately after the birth of the second pup and the subsequent course of parturition was recorded in a total of 80 rats. Both s.c. morphine (10 mg/kg) and intracerebroventricular (i.c.v.) morphine (18 micrograms through a previously implanted cannula) interrupted parturition, delaying the birth of the sixth pup after treatment to 187.3 +/- 35.9 (S.E.M.) min and 195.4 +/- 19.5 min respectively, compared with 46.4 +/- 3.7 and 66.1 +/- 17.5 min after vehicle alone. The dose of morphine given i.c.v. had no effect when given s.c. Naloxone given concurrently prevented the effects of morphine. Eventually the rate of parturition in the morphine-treated groups recovered. Perinatal pup mortality rate was not increased when morphine was given to the mothers, but it did inhibit the expression of normal intrapartum maternal behaviour. Pup mortality was increased 48 h post partum by morphine given during parturition, and it reduced the proportion of rats with normal maternal behaviour 24 h post partum. Morphine did not affect spontaneous or oxytocin-stimulated contractile activity of the parturient uterus in vitro. The concentration of oxytocin in trunk blood plasma was decreased 40 min after i.c.v. morphine (24.3 +/- 3.9 vs 39.3 +/- 6.5 pmol/l in controls), as was vasopressin (7.2 +/- 1.5 vs 19.7 +/- 4.5 pmol/l in controls). Intravenous infusion of oxytocin (2-5 mU/min for 144.3 +/- 8.2 min; total infused 448.5 +/- 61.9 mU) after i.c.v. morphine re-started parturition; all pups were born to these rats (mean time to pup 6, 110.3 +/- 12.7 min) before the i.v. vehicle-infused rats given i.c.v. morphine re-started (mean time to pup 6, 406.3 +/- 125.2 min). It is concluded that morphine given during parturition acts centrally through opioid receptors to inhibit oxytocin secretion, and impairs the expression of maternal behaviour. Reversal of the effects of morphine on parturition by i.v. oxytocin demonstrates the important role of oxytocin in fetus ejection and expulsion.

Animals↗
PubMed2005

Predicting time of parturition from changing vaginal temperature measured by data-logging apparatus in beef cows with twin fetuses.

Vaginal temperatures (VT) of crossbred (Japanese Black crossed Holstein-Friesian) beef cows (n = 31) were measured by a data-logging apparatus to obtain serial data from days 0 to 6 before parturition. For both single and twin pregnancies, no significant differences were observed in VT during days 3-6 before parturition. Maternal VT was not affected by maternal weight just after parturition, parity, fetal sex, or total fetal litter weight. Average of twin litter weights for two males (MM) and two females (FF) had the strong positive correlations (r = 0.84; P < 0.05) with maternal VT, whereas twin weights of mixed-gender twins (FM) did not correlate with maternal VT (r = -0.26; P = 0.61). Maternal temperature decreased as weights of the female fetus of FM twins became heavier (r = -0.82; P < 0.05). In contrast, maternal VT of FF and MM twins increased as twin weights increased. We defined when the VT began to decrease before parturition by two different methods. One was the "same hours method" where differences in VT between a particular time of day and the corresponding time of the preceding day were compared when the VT was consistently > or =0.3 or > or =0.5 degrees C for more than 3h. The second method was the "maximum-minimum method" where decreased in the maximum or the minimum values of the day over > or =0.3 and > or =0.5 degrees C were compared to values of preceding day. Onset of decreased VT before expulsion was not different between singletons and twins. In an attempt to define the critical condition in predicting parturition, we estimated assumable predicting probability using the 31 cows that were collected VT. When the parturition occurred within 60 h in the "same hours method" and 72 h since VT was > or =0.3 degrees C and in the "maximum-minimum method", the assumable probability was 100%. In verification experiment under these condition, the "same hours method" had a higher probability of predicting the time of parturition than the "maximum-minimum method", and it was possible to detect the onset of decreased VT at the correct time by the minutes. We concluded that "same hours method" was useful for predicting parturition time in cattle with single and twin pregnancies by the serial measurement of vaginal temperature.

Animals↗
PubMed2006

Influence of induction of parturition on the neonatal acute phase response in foals.

The objectives of the present study were to determine whether induction of parturition in mares at term with low doses of oxytocin (2.5 i.u. i.v. every 20 min) affected the incidence of peri-partum complications or inflammatory responses in the neonatal foal. Parturition was induced in 11 of 26 mares and the remainder foaled spontaneously. Serum concentrations of amyloid A (AA; an acute phase protein) were measured (with a commercial ELISA) from 0 to 72 h postpartum in 18 of the neonatal foals. The incidence of dystocia and premature placental separation was higher in induced mares (2 of 11 and 1 of 11 versus 0 of 15 and 0 of 15, respectively), whereas retained fetal membranes were more common in spontaneous foalings (2 of 15 versus 0 of 11). When abnormal foals were excluded (to decrease the influence of endogenous serum AA elevations), serum concentrations of AA increased to the same extent over time in foals with induced versus spontaneous parturition; foals with spontaneous parturition had a mean serum AA concentration of 7.8 microg/mL at birth that increased to a maximum of 58.9 microg/mL at 36 h; foals with induced parturition had a mean serum AA concentration of 5.4 microg/mL at birth that increased to a maximum of 41.4 microg/mL at 48 h. Baseline serum AA concentrations were lower in induced foals. We concluded that inducing parturition with low doses of oxytocin in mares at term did not affect (relative to spontaneous parturition) the temporal dynamics of serum AA concentrations in the normal foal in the first 72 h of life. However, the induction procedure may lead to complications during parturition that, if not detected early, could result in the development of an inflammatory response in the neonate.

Acute-Phase Reaction↗
PubMed1998

Induction and potentiation of parturition in fingernail clams (Sphaerium striatinum) by selective serotonin re-uptake inhibitors (SSRIs).

Parturition in fingernail clams (Sphaerium spp.) can be induced by external application of serotonin and serotonergic ligands. Selective serotonin re-uptake inhibitors (SSRIs) increase neurotransmission at serotonergic synapses by blocking re-uptake transporters. We tested the efficacy of SSRIs (fluvoxamine, fluoxetine, paroxetine) at inducing parturition in the fingernail clam Sphaerium striatinum. Parturition was induced by fluvoxamine and paroxetine, but only potentiated by fluoxetine. Fluvoxamine was potent, significantly inducing parturition at concentrations from 10 nM to 100 microM compared with negative controls. Fluvoxamine also significantly potentiated a subthreshold (10 microM) concentration of serotonin. Paroxetine also induced parturition but was less potent. Only 10 microM paroxetine significantly induced parturition compared with controls. Fluoxetine (1-100 microM) did not induce any parturitions, but at 5 microM it potentiated parturition in subthreshold serotonin concentrations as low as 50 nM. These results suggest the presence of serotonin re-uptake transporters in bivalve molluscs and may provide a way of stimulating serotonergic mechanisms without using serotonin or its ligands.

Animals↗