Plasma oxytocin and oxytocin neurone activity during delivery in rabbits

The extracellular electrical activity of magnocellular neurones was recorded from unanaesthetized, unrestrained rabbits in birth and the post partum suckling period. The activity of oxytocin neurones was differentiated from that of vasopressin cells on the basis of their stereotyped activity in suckling. Oxytocin neurones showed five to fourteen discrete bursts of accelerated discharge in parturition. Each burst lasted 2-22 s and represented a 3-100-fold increase in the rate of firing, compared with pre-partum values, and was followed 10-34 s later by delivery. After parturition, the spontaneous activity of these neurones returned to pre-partum rates of firing. Vasopressin neurones did not show any bursts of discharge in delivery. There was a significant fall in the discharge frequency compared with pre-partum levels (P less than 0.05: Student's t test) and a significant (P less than 0.01) lengthening of the modal interspike interval. Serial blood samples were obtained during parturition in ten rabbits. Simultaneous recordings of magnocellular neurones activity and plasma oxytocin measurements were made in four of these experiments. Plasma oxytocin profiles were related to the observed events of parturition. Frequent blood samples (0.2-0.3 ml every 10-15 s) were taken throughout delivery and plasma oxytocin measured by sensitive radioimmunoassay in unextracted plasma (lower limit sensitivity of assay 5 pg ml-1). Before birth, plasma oxytocin was 53 +/- 12 pg ml-1 (mean +/- S.E. of mean) and rose to 2846 +/- 326 pg ml-1 within 40-120 s of the onset of the expulsive phase of delivery. Peak concentrations of oxytocin were coincident with delivery of the first or second fetus. No sign of pulsatile release of oxytocin was demonstrated in the profiles but significantly (P less than 0.001) greater variance in oxytocin titres was found during birth compared with pre-partum values which is suggestive of pulsatile release. There was a straight line relationship between peak oxytocin concentrations in the plasma and the speed of delivery, implying that oxytocin facilitates as well as maintains labour in the rabbit

The dipsogenic effects of rat relaxin: The effect of photoperiod and the potential role of relaxin on drinking in pregnancy

Experiments were done to examine whether rat relaxin is dipsogenic and whether such dipsogenic effects of rat relaxin are related to time of injection during the light-dark cycle. Female rats were fitted with a chronic intra-cerebro-ventricular (icy) cannula. Rat relaxin (2.5, 5, 10, 25, 50, or 100 ng/2 μl in 0.9% saline) was injected into the right lateral ventricle at either morning (0800-1000 h), afternoon (1400-1600 h), or night (2200-2400 h), and water consumption was measured. Relaxin caused a dose-dependent dipsogenesis at doses ≥ 5 ng, but the sensitivity and magnitude of the response varied with the photoperiod. Water consumption was smallest (3.5 ± 0.7 ml at 50 ng) and least sensitive (minimal effective dose at 25 ng) in the afternoon and maximal (17.7 ± 2.3 ml at 50 ng) and most sensitive (minimal effective dose 5 ng) at night. The latency from injection to drinking was 55.8 ± 10.4 sec (mean ± SEM) and did not vary significantly with either the dose or time of day. A second set of experiments was done to examine the effects of neutralizing the central actions of relaxin on drinking behavior in pregnancy. Pregnant rats were injected daily, through a chronically implanted icv cannula, with either a specific monoclonal antibody raised against rat relaxin from day 12 to day 22 of gestation or with saline as a control. Drinking and eating behavior and weight gain were monitored every 12 h during pregnancy. There was a significant decrease in water consumed at night, but no effect on drinking during the day in relaxin-neutralized rats. These animals also showed a decrease in weight gain during pregnancy compared with controls and gave birth to lighter-weight litters. These data provide evidence that the dipsogenic response to exogenous rat relaxin in female rats varies with time of injection during the light-dark cycle and suggest that relaxin in the brain may have a role in nighttime drinking behavior during the second half of pregnancy

Randomized controlled trial assessing the efficacy of a reusable fish-shaped iron ingot to increase hemoglobin concentration in anemic, rural Cambodian women

First published online June 14, 2017Background: Anemia affects 45% of women of childbearing age in Cambodia. Iron supplementation is recommended in populations in which anemia prevalence is high. However, there are issues of cost, distribution, and adherence. A potential alternative is a reusable fish-shaped iron ingot, which, when added to the cooking pot, leaches iron into the fluid in which it is prepared.Objective: We sought to determine whether there was a difference in hemoglobin concentrations in rural Cambodian anemic women (aged 18-49 y) who cooked with the iron ingot or consumed a daily iron supplement compared with a control after 1 y.Design: In Preah Vihear, 340 women with mild or moderate anemia were randomly assigned to 1) an iron-ingot group, 2) an iron-supplement (18 mg/d) group, or 3) a nonplacebo control group. A venous blood sample was taken at baseline and at 6 and 12 mo. Blood was analyzed for hemoglobin, serum ferritin, and serum transferrin receptor. Hemoglobin electrophoresis was used to detect structural hemoglobin variants.Results: Anemia prevalence was 44% with the use of a portable hemoglobinometer during screening. At baseline, prevalence of iron deficiency was 9% on the basis of a low serum ferritin concentration. There was no significant difference in mean hemoglobin concentrations between the iron-ingot group (115 g/L; 95% CI: 113, 118 g/L; P = 0.850) or iron-supplement group (115 g/L; 95% CI: 113, 117 g/L; P = 0.998) compared with the control group (115 g/L; 95% CI: 113, 117 g/L) at 12 mo. Serum ferritin was significantly higher in the iron-supplement group (73 μg/L; 95% CI: 64, 82 μg/L; P = 0.002) than in the control group at 6 mo; however, this significance was not maintained at 12 mo (73 μg/L; 95% CI: 58, 91 μg/L; P = 0.176).Conclusions: Neither the iron ingot nor iron supplements increased hemoglobin concentrations in this population at 6 or 12 mo. We do not recommend the use of the fish-shaped iron ingot in Cambodia or in countries where the prevalence of iron deficiency is low and genetic hemoglobin disorders are high. This trial was registered at clinicaltrials.gov as NCT02341586.Aviva I Rappaport, Kyly C Whitfield, Gwen E Chapman, Rickey Y Yada, Khin Meng Kheang, Jennie Louise, Alastair J Summerlee, Gavin R Armstrong, and Timothy J Gree