Prolactin mediates behavioural rejection responses to avian brood parasitism

Adaptations resulting from co-evolutionary interactions between avian brood parasites and their hosts have been extensively studied, yet the physiological mechanisms underlying antiparasitic host defences remain little known. Prolactin, one of the main hormones involved in the regulation of avian parental behaviour, might play a key role in the orchestration of the host responses to avian brood parasitism. Given the positive association between prolactin and parental behaviour during incubation, decreasing prolactin levels are expected to facilitate egg-rejection decisions. We tested this prediction by implanting Eurasian blackbird (Turdus merula) females with an inhibitor of prolactin secretion, bromocriptine mesylate, to experimentally decrease their plasma prolactin levels. Bromocriptine-implanted individuals ejected mimetic model eggs at higher rates, and showed shorter latency to egg ejection, than placebo-treated birds. To our knowledge, this is the first experimental evidence that behavioural host defences against avian brood parasitism are mediated by prolactin.

Endocrine, energy, and lipid status during parturition and early lactation in indigenous goats native to the Algerian Sahara

Background and Aim: Goats are widely distributed in southwest Algeria. The Saharan goat is perfectly adapted to the harsh conditions of arid areas, and it is characterized by resistance to long photoperiod and reduced metabolic needs, allowing the survival of its offspring by maintaining lactation. Several studies have demonstrated that parturition and lactation are critical periods that induce hormone, energy, and lipid status changes in mammals. However, the relationship between the blood biochemical parameters of parturition control and lactation functions in the Algerian Saharan goat has not been thoroughly documented. Therefore, this study assesses hormone and metabolite levels during parturition and early lactation in Saharan goats reared in arid areas. Materials and Methods: Experiments were performed on 14 multiparous female goats, and blood samples were collected during parturition, 4 days postpartum (D1PP-D4PP), and during the first 12 weeks of lactation (W1-W12) to analyze prolactin, cortisol, glucose (GLU), total proteins (TP), cholesterol (CHO), triglycerides (TGs), total lipids (TL), low-density lipoproteins (LDLs), high-density lipoproteins (HDLs), and very LDLs (VLDLs). Results: Statistical data analysis revealed a significant (p<0.05) increase in plasma prolactin concentrations at W1 after parturition, reaching maximum values at W3 and W9, and remained high until W12 of lactation. Plasma cortisol levels were high at parturition, reaching two peaks at W3 and W9, and then decreased at W5, W7, and W12 of lactation. No significant changes were found in serum GLU levels during the first 7 weeks of lactation compared with parturition day; then, the levels became significantly (p<0.05) lower at W8, W11, and W12 of lactation. Plasma TP increased significantly (p<0.05) at D3PP, W1, and W4, then decreased significantly (p<0.05) at W8. In addition, this decrease coincided with that of GLU production. Serum CHO, TGs, TL, LDLs, and VLDLs, were low at parturition and high at D4PP and during the first 3 months of lactation. Furthermore, HDL levels were low at D3PP, 1st, and 3rd months and high at the 2nd month of lactation. Conclusion: This study emphasized the impact of parturition and the 1st weeks of lactation on endocrine and metabolic changes in indigenous goats living in the Algerian Sahara Desert. These results can be used to monitor and improve farming management and understand physiological adaptive strategies, mainly lactation function sustainability, of this goat living in marginal zones.

Case-Control study of prolactin and placental lactogen in SGA pregnancies

Prolactin and placental lactogens increase during pregnancy and are involved with many aspects of maternal metabolic adaptation to pregnancy, likely to impact on fetal growth. The aim of this study was to determine whether maternal plasma prolactin or placental lactogen concentrations at twenty weeks of gestation were associated with later birth of small-for-gestational-age babies (SGA). In a nested case-control study, prolactin and placental lactogen in plasma samples obtained at 20 weeks of gestation were compared between 40 women who gave birth to SGA babies, and 40 women with uncomplicated pregnancies and size appropriate-for-gestation-age (AGA) babies. Samples were collected as part of the “Screening of Pregnancy Endpoints” (SCOPE) prospective cohort study. SGA was defined as birthweight < 10th customised birthweight centile (adjusted for maternal weight, height, ethnicity, parity, infant sex and gestation age) in mothers who remained normotensive. No significant differences were observed in concentrations of prolactin or placental lactogen from women who gave birth to SGA babies compared with women with uncomplicated pregnancies. However, a sex specific association was observed in SGA pregnancies, whereby lower maternal prolactin concentration at twenty weeks of gestation was observed in SGA pregnancies that were carrying a male fetus (132.0  46.7 ng/ml vs 103.5  38.3 ng/ml, mean ± SD, p=0.036 Student’s t-test) compared to control pregnancies carrying a female fetus. Despite the implications of these lactogenic hormones in maternal metabolism, single measurements of either prolactin or placental lactogen at 20 weeks of gestation are unlikely to be useful biomarkers for SGA pregnancies.

Effects of blue monochromatic light directed at one eye of pregnant horse mares on gestation, parturition and foal maturity

Blue light directed at one eye advances the equine ovulatory season but can also advance foaling. In this study, effects of blue LED light on pregnancy outcome were assessed. Twenty mares with singleton pregnancies were studied over two consecutive years in a cross-over design. In one year, mares received an extended photoperiod using 50 lux of blue LED light (468 nm) directed at a single eye from 08:00 until 23:00 daily via head-worn light masks starting mid-December and in the other year remained untreated as controls. Gestation was shorter in blue LED light-treated (333.2+/- 1.0 days, +/- SEM) than in control pregnancies (337.9+/-1.8 days, p<0.05). Colostral IgG content was lower in treated than in control pregnancies (p<0.05) but was adequate to ensure sufficient IgG transfer to newborn foals with a single exception. Foals born to blue LED light-treated mares had lower wither heights (102.5+/-1.1 vs. 105.2+/-1.0 cm, p<0.01), similar weights (55.0+/-1.3 vs. 55.5+/-1.1 kg) and took less time to stand after birth than control foals (39+/-3 vs. 56+/-4 min, p<0.05). The neutrophil/lymphocyte ratio, was higher in foals born to blue LED light-treated mares than controls (3.2+/-0.2 vs. 2.7+/-0.2; p<0.05). Foals born to blue LED light-treated mares had reduced hair length compared to controls (13.1+/-0.8 vs. 20.9+/-0.1 mm; p<0.001) and hair regrowth in treated mares was reduced (p<0.05). Maternal plasma prolactin concentration was increased in treated mares (p=0.05) and peaked at foaling (p<0.001). In conclusion, blue LED light directed at one eye advanced foaling and influenced height, hair coat and maturity in foals.

Failing Memory in Nonaffective Psychosis and Prolactin Response to 12.5 µg i.v. TRH

Dear EditorThe increase in plasma prolactin at 15 min following administration of 12.5 µg TRH i. v. (∆prol) was introduced in Pharmacopsychiatry as an inverse estimate of tuberoinfundibular dopamine (TIDA) activity 1. We used the unpublished data set in 20 participants with nonaffective psychosis from our 1991 study utilizing ∆prol 2 and here report new results with its association with memory.

Influence of Pre-Mating Plasma Prolactin Profile on Reproductive Performance of California Doe Rabbits

Ovulation failure was associated with a reduction in pre-mating concentrations of oestradiol-17&beta; and prolactin (PRL). The present study aimed to evaluate whether pre-mating PRL levels have a role on the reproductive efficiency of doe rabbits. A total of 78 multiparous California does (2nd parity) were divided, according to plasma pre-mating PRL, into five categories, &gt;20-25, &gt;25-30, &gt;30-35, &gt;35-40, and &gt;40-45 ng/ml. Does in all categories were naturally mated and kindled, then their reproductive measurements and progesterone (P4) levels were determined. Results show that pre-mating PRL averaged 23.60&plusmn;0.78, 28.00&plusmn;0.83, 33.46&plusmn;0.43, 38.17&plusmn;0.49 and 41.98&plusmn;0.68 ng/ml in five categories (p &lt; 0.05), respectively, representing the highest distribution (38.5%) in the 3rd-category. Live body weight of doe rabbits, at mating, pregnancy, and parturition increased (p &lt; 0.05) with increasing pre-mating PRL level. The number of services, litter size, and pregnancy rate increased (p &lt; 0.05) by increasing PRL levels. Reproductive traits and P4 level at mid-pregnancy of does, and average weight of kits at birth increased (p &lt; 0.05) by increasing PRL levels. The pre-mating PRL profile is important for the identification of reproductive performance in doe rabbits.