Plasma Prolactin Concentrations Research Articles

Effect of the Prolactin Inhibitor Cabergoline and the Gonadotropin Releasing-Hormone Agonist Deslorelin in the Suppression of Plasma Prolactin Concentrations and Egg Laying in Quail (Coturnix japonica)

Egg binding and excessive laying frequently affect avian patients, and in many cases the treatment includes suppression of egg production. Currently, for the suppression of egg production in avian patients, a gonadotropin-releasing hormone agonist, in the form of a deslorelin implant, is often used. However, the commercially available deslorelin implants have an undesired delayed onset, as well as a potential brief increase in gonadotropin secretion after administration ("flare-up" effect) that can lead to oviposition before the actual suppression of gonadotropins. The objective of this study was to investigate whether the prolactin inhibitor cabergoline suppresses ovulation and whether it could be used to bridge the time until the onset of effect by the deslorelin implant. We measured the effect of cabergoline (30 µg/kg PO q24h × 14 days), deslorelin implants (4.7 mg SC), and a combination of both on egg laying and plasma prolactin concentrations in 37 quail (Coturnix japonica) over 6 weeks. Quail were divided into 4 groups: group DesCab (deslorelin implant and cabergoline oral; n = 9); group DesPlac (deslorelin implant and placebo oral; n = 9); group PlacCab (placebo implant and cabergoline oral; n = 9); and group PlacPlac (placebo implant and placebo oral; n = 10). Regular egg laying stopped in 100% (9/9) of birds in group DesCab and 78% (7/ 9) of birds in group DesPlac within 5 days of placing the deslorelin implant. No bird ceased egg production in group PlacCab (0/9), and 10% of birds ceased egg production intermittently in group PlacPlac (1/10). Treatment with the deslorelin implant (P < .001) and with cabergoline (P = .04) had a significant (negative) influence on plasma prolactin concentrations compared with the baseline. The interaction of deslorelin and cabergoline treatment, as well as time after initiation of treatment, did not have a significant effect on plasma prolactin concentrations. These results show that daily oral cabergoline has no significant influence on egg laying and only a minor biologically nonsignificant effect on lowering the relative plasma prolactin concentrations in quail.

Maternal prolactin levels during late pregnancy and nurturing behavior of offspring in mice.

Elucidating the mechanisms underlying nurturing and neglect behaviors is meaningful but challenging. Recently, we found that CIN85-deficient mice had reduced pituitary hormone prolactin secretion during late pregnancy, and their pups later showed an inhibited nurturing behavior. To examine whether this phenomenon could be reproduced in normal mice and not just CIN85-deficient mice, we investigated the nurturing behavior of offspring born to mothers whose blood prolactin levels had been reduced by bromocriptine administration during late pregnancy. First, to determine when bromocriptine treatment should be started, we investigated the detailed changes in blood prolactin levels in late pregnancy in mice, resulting in the identification of the prepartum prolactin surge. Furthermore, prolactin receptors in the fetal hypothalamus were expressed to the same extent as in the adult hypothalamus. Treatment with bromocriptine decreased the plasma concentrations of prolactin to the basal range throughout late pregnancy. However, against expectations, the proportion of the resultant pups exhibiting nurturing behaviors as adults was as high as that in the mice without bromocriptine treatment. In conclusion, the elimination of prolactin secretion during late pregnancy alone does not induce neglect-like behavior in offspring, suggesting that CIN85-deficient mice appear to involve another factor due to CIN85 deficiency besides prolactin deficiency.

Plasma levels of luteinizing hormone and prolactin in relation to double brooding in Great Tit (Parus major)

The reproductive behaviors of birds are mainly controlled by the hypothalamus-pituitary-gonad axis. Many studies have shown that reproductive hormones are tightly linked to the breeding sub-stages. However, only a few studies have examined the temporal trend of hormone levels among different reproductive stages in multiple brooded species. We investigated the changes in plasma luteinizing hormone (LH) and prolactin (PRL) concentrations during different reproductive stages of the facultative double-brooded Great Tit (Parus major). We found that the concentrations of LH and PRL in females were significantly higher than those in males. Females had significantly higher LH and lower PRL concentrations in the pre-breeding period than in the first/second brooding periods, and there were no significant changes between the first and second brooding periods. The concentrations of LH and PRL in males had no significant difference between the pre-breeding period and the first brooding periods, while LH and PRL concentrations in the second brooding period were significantly higher than those in the first brooding period. We conclude that there are sex-based differences between LH and PRL at different stages of reproduction. The changes in LH and PRL in both males and females should be related to their physiological functions. Especially for males, individuals with higher levels of LH and PRL are more likely to maintain second clutches.

Pituitary and ovarian hormones: is their plasma concentration affected by litter size in primiparous lactating rabbit does?

Genetic selection in commercial rabbit lines based on litter size has positively improved the number of kits suckling, presumably to weaning. Although it has been proven that the energetic balance of primiparous does is due to the need to satisfy pregnancy, lactation and growth requirements, litter size adjustment from 7 to 12 kits is applied as a routine in commercial rabbit farms. The suckling stimulus provokes a prolactin (PRL) secretion, which in turn can modulate the preovulatory release of luteinising hormone (LH) and, consequently, the ovulatory and productive responses of the does. This study aimed to determine if litter size of prolific primiparous rabbit does during lactation [Group HL, with high litter density (10-12 kits; n=21) and Group LL, with low litter density (7-9 kits; n=29)] influences plasma concentration of PRL. Blood samples from lactating does were taken weekly throughout lactation starting on day 4 post-partum, until day 32 post-partum, before and immediately after suckling. In addition, the does were re-inseminated after weaning (day 32 post-partum), and sampled at 0 and 60 min after induction of ovulation to determine whether litter size affected the peak of LH, progesterone (P4) concentrations and the main productive parameters of their second pregnancy. All hormones were determined by enzyme immunoassay. Statistical analysis of the results revealed that the PRL concentrations of hyperprolific rabbit does before and immediately after a suckling stimulus from 7-9 or 10-12 kits were significanltly different, as we only detected basal levels, with a rise after weaning in both groups. More studies are necessary, delaying blood sampling to later periods of time after the suckling stimulus, in order to conclude whether the peak release of this hormone is altered or not. There were also no differences in plasma LH and progesterone levels after artificial insemination, or in productive performance of these females after their second pregnancy. In conclusion, the litter size adjustment of prolific primiparous rabbits with 7 to 12 kits determines adequate pituitary, ovarian and reproductive responses at second parturition if the does are inseminated after weaning.

Effects of thermal stress on physiological state and hormone concentrations in Holstein cows under arid climatic conditions

This study was conducted to investigate the effect of heat stress on the physiology of dairy cows and to detect the relationship between rectal temperature (RT) and respiration rate (RR), heart rate (HR), and plasma concentrations of cortisol, thyroxine, and prolactin. During the experiment, 44 Holstein cows were allocated to two groups for each season. The average temperature-humidity index (THI) values were 55 ± 2.31 in winter and 78 ± 1.9 in summer. As the THI values increased from 55 to 78, RR rose by 35 inspirations per minute, HR by 3 beats per minute, and RT by 1.2 °C. In addition, the average concentration of cortisol increased from 19.30 to 21.04 nmol/L, and prolactin from 58.52 to 129.79 ngm/L, whereas free thyroxine decreased from 15.43 to 14.01 pmol/L. Plasma sodium and potassium concentrations were similar in the two seasons. These results confirmed that RT is an indicator of the response in dairy cows to hot environmental temperatures. However, they also showed signs of stress, which were reflected in higher levels of cortisol and in certain physiological responses.

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 20 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 customized 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 20 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 ± s.d., P = 0.036 Student’s t-test) compared to control pregnancies carrying a male 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.Lay summaryEarly identification during pregnancy of small for gestational age (SGA) babies would enable interventions to lower risk of complications around birth (perinatal), but current detection rates of these at risk babies is low. Pregnancy hormones, prolactin and placental lactogen, are involved in metabolic changes that are required for the mother to support optimal growth and development of her offspring during pregnancy. The levels of these hormones may provide a measurable indicator (biomarker) to help identify these at risk pregnancies. Levels of these hormones were measured in samples from week 20 of gestation from women who went on to have SGA babies and control pregnancies where babies were born at a size appropriate for gestation age. Despite the implications of prolactin and placental lactogen in maternal metabolism, no significant differences were detected suggesting that single measures of either prolactin or placental lactogen at 20 weeks gestation are unlikely to be useful biomarker to help detect SGA pregnancies.

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.

Relationship of Prolactin Concentrations to Steady-State Plasma Concentrations of Aripiprazole in Patients With Schizophrenia.

Aripiprazole is regarded as the first-line antipsychotic medication. Long-term aripiprazole therapy can cause hypoprolactinemia, which may result from its activity as a dopamine agonist. However, there is little information on hypoprolactinemia and steady-state aripiprazole concentrations. The subjects included 66 male and 177 female patients diagnosed with schizophrenia who were treated with aripiprazole. The plasma concentrations of aripiprazole and dehydroaripiprazole and the plasma concentration of prolactin were measured using high-performance liquid chromatography and enzyme immunoassay, respectively. A prolactin concentration of <5 ng/mL was defined as hypoprolactinemia. Fifty-two of the 66 male patients (79%) and 58 of the 177 female patients (33%) had hypoprolactinemia. There were significant inverse correlations between plasma prolactin levels and plasma concentrations of aripiprazole (rs = -0.447, P < 0.001) and the active moiety (aripiprazole plus dehydroaripiprazole) (rs = -0.429, P < 0.001) in men. In women, significant inverse correlations were also found between plasma prolactin levels and plasma concentrations of aripiprazole (rs = -0.273, P < 0.01) and the active moiety (rs = -0.275, P < 0.01). These findings suggest that lower prolactin levels are, to some extent, associated with higher plasma drug concentrations in male and female patients with schizophrenia treated with aripiprazole.

The Effects of Furosemide on Behavioral and Hormonal Parameters in Male and Female Mice Subjected to Immobilization and Cold-Water Stress.

IntroductionThe diuretic agent furosemide (FUR, 25 and 50 mg/kg) has been shown in a single report to act as an anti-stressor agent in two models of acute stress in mice, viz. electric foot–shock stress and immobilization (IMS). The present work aimed to investigate the possible anti-stressor action of FUR on two models of acute stress in mice, cold-water stress (CWS) and IMS, and tried to determine whether gender has any impact on the effect of FUR.MethodsFUR (40 mg/kg) was injected intraperitoneally, and after 30 minutes, mice were subjected to CWS (4°C for three minutes) or IMS (fixing movement for two and a half hrs using adhesive tape). Motor and exploratory activities, neuromuscular coordination, and thermal nociception were then tested. Blood was collected from the mice and used to measure the concentrations of three stress hormones (corticosterone, epinephrine and prolactin).ResultsMice subjected to CWS and IMS had significantly reduced motor and exploratory activities, neuromuscular coordination, and increased nociception. CWS and IMS also significantly increased the plasma concentrations of the three hormones. FUR pretreatment significantly mitigated these stress-induced hormonal changes. There was no significant sex difference when CWS or IMS was applied.DiscussionIMS and CWS stimuli in male and female mice caused significant elevations in the plasma concentrations of corticosterone, epinephrine, and prolactin, accompanied by a significant reduction of motor and exploratory activities, neuromuscular coordination, and thermal nociception. There were no sex differences when IMS was applied. In stressed mice, prior administration of FUR (40 mg/kg) significantly decreased the concentrations of stress hormones, and this effect significantly mitigated the stress-induced behavioural and motor changes.

New insights of prolactin in humans: the role of nurses

Prolactin is synthesize by the anterior pituitary gland, by extrapituitary tissues, such as the mammary gland, prostate, skin and brain. It has been relateding to lactogenesis, however, it is known to induce a wide range of functions in different tissues, modulating neurogenesis, neurodevelopment, sleep, learning, memory and homeostasis of the immune system, and may be linked to different types of cancers. The objective was to identify the new insights of the prolactinemia as a biomarker or inducer of pathological processes. During lactation, prolactin promotes milk synthesis and oxytocin stimulates ejection, its increase may come from mechanisms such as nipple sucking stimulus, stress, sexual activity, protein intake, unregulated menstrual cycle and pregnancy, pharmacological or pathological origins. Prostate and breast cancers can be treated using methods to antagonize the PRL receptor and its signaling pathways, which include small molecule-based antagonists of proteins. Drugs to lower the plasma concentration of prolactin are strong candidates to be test in reuse clinical trials to improve the cognitive skills of patients with mood disorder and schizophrenia. Keeping up to date on research, in addition to seeking to evaluate all the variables and biomarkers available for the case, can increase the chance of making an early diagnosis.

19 Interaction of kisspeptin and the somatotropic and lactotropic axes in mares and geldings

Several experiments were conducted to investigate the interaction between kisspeptin and the somatotropic and lactotropic axes in mares and geldings. Light horse, diestrous mares and geldings, weighing approximately 500 kg and aged 6 to 24 years, were randomly assigned to treatment with 1 mg equine kisspeptin-10 (Kp10; n = 10) or 1 mL saline (n = 9), i.v. Blood samples were collected via jugular venipuncture −10, 0, 5, 10, 15, 20 and 30 min relative to treatment. Plasma concentrations of growth hormone (GH) and prolactin (PRL) were determined by RIA and means compared using ANOVA with repeated sampling. Neither GH nor PRL were stimulated by Kp10. In a second experiment, 30 mares and geldings were used to determine if pre-treatment with estradiol or progesterone would elicit a GH or PRL response to Kp10. Five mares and 5 geldings each were assigned to pre-treatment with 50 mg estradiol cypionate in oil (ECP), 600 mg long-acting progesterone, or oil only, i.m. Two days later, all horses received 1 mg Kp10 in saline, i.v., and blood sampling occurred 0, 5, 10, 15 and 20 min relative to Kp10 administration. Mean GH and PRL concentrations and area under the curve were compared by ANOVA. No stimulation of GH or PRL was observed. In a third experiment, 12 diestrous mares, confirmed by plasma progesterone and ultrasound findings, were randomly assigned to treatment with 1 mg Kp10 (n = 6) or 1 mL saline (n = 6) followed by the dopamine antagonist, sulpiride (0.01 mg/kg body weight), 5 min later. Blood sampling occurred 0, 5, 10 and 15 min relative to sulpiride administration. Sulpiride stimulated PRL ( P < 0.0001) in both groups of mares; however, PRL concentrations were lower ( P ≤ 0.01) in Kp10-treated mares compared with saline-treated mares. To determine if estrogen altered the PRL response to sulpiride, 12 seasonally anovulatory mares, confirmed by plasma progesterone and ultrasound findings, were used in a fourth experiment and randomly assigned to receive 50 mg ECP (n = 6) or oil (n = 6), i.m. The next day, mares were challenged with sulpiride. Treatment and blood sampling occurred as described in experiment 3. Plasma PRL was stimulated ( P < 0.001) in both groups of mares and responses were similar between treatments. In the described experiments, 1 mg Kp10 given as a bolus failed to stimulate circulating GH or PRL within 30 min in mares or geldings regardless of steroid milieu. This is in contrast to reports of GH stimulation in ruminants. Kp10 did alter the PRL response to sulpiride in diestrous mares, perhaps suggesting an interaction between Kp10 and dopaminergic input to the pituitary in a progesterone dominant environment.

Role of changes in plasma prolactin concentrations on ram and buck sperm cryoresistance

Seasonal endocrine changes may modify sperm cryoresistance in certain small ruminant species. The present work examines the effect of prolactin (PRL) on ram and buck sperm cryoresistance. A dopamine agonist (bromocriptine [BCR] 60 mg i.m. twice per week from May 15 to June 15, that is, approaching the summer solstice) or antagonist (sulpiride [SLP] 100 mg s.c. daily from December 15 to January 15, that is, around the winter solstice) was administered under solstice-appropriate photoperiod conditions to modify PRL secretion. Control animals received the vehicle only. Compared to the corresponding controls, BCR reduced PRL secretion to basal levels in both the rams and bucks. In rams, the cryoresistance ratios for sperm curvilinear velocity (P < 0.05) and lateral head displacement (P < 0.01) were higher for the BCR-treated animals. In bucks, neither the characteristics of fresh nor frozen-thawed sperm were affected by BCR treatment. After the administration of SLP, PRL levels increased and remained high for more than 5 h in the rams though they immediately began to fall in the bucks. By 24 h, PRL had returned to basal concentrations in both species. In rams treated with SLP, the cryoresistance ratios for sperm progressive motility, straight line velocity, sperm mean path velocity, cross beat frequency, and the progression ratios linearity, straightness and oscillation, were all lower compared to the controls (P < 0.05), while the amplitude of lateral head displacement was higher (P < 0.01). In bucks, sperm cryoresistance was not affected by SLP administration. Together, these results suggest that high levels of PRL negatively affect the cryoresistance of ram sperm, while buck sperm seems unaffected.

Delta-Opioid Receptors Play a Role in the Control of Selected Parameters Related to Stress and Brain Plasticity Under Non-stress and/or Stress Conditions.

There is some evidence that delta-opioid receptors may be involved in the brain processes related to neuroprotection. The aim of the present studies was to test the hypothesis that endogenous opioid peptides acting via delta-opioid receptors can protect against stress-induced changes in factors related to brain plasticity and stress hormone release. Forty male adult Wistar rats were used. Half of the animals were exposed to sustained partial restraint stress (hypokinesis) lasting48h. Rats were treated with vehicle (isotonic saline) or the delta-opioid receptor antagonist naltrindole (3mg/kg/ml, s.c.) six times a day. The stressfulness of the model was confirmed by increased plasma concentrations of corticosterone and prolactin, the increase in anxiety behavior in the open field test, as well as the reduction of BrdU incorporation into newly formed DNA in the hippocampus. Treatment with naltrindole potentiated the stress-induced rise in aldosterone concentrations. The blockade of delta-opioid receptors resulted in a decrease in hippocampal BDNF gene expression independently of control or stress conditions. Treatment with naltrindole enhanced plasma concentrations of copeptin, a stable precursor of vasopressin. In conclusion, these results suggest that endogenous opioid peptides might play an inhibitory role in aldosterone release under stress conditions and in the control of vasopressin release independently of stress exposure. Endogenous opioids might stimulate hippocampal gene expression of the important neurotrophic factor BDNF via delta-opioid receptors.

Local anesthetic added to spinal anesthesia; does it stabilize stress hormones after inguinal herniorrhaphy?: A randomised controlled trial

BackgroundElective inguinal hernia repair is a common minor surgery. Early postoperative mobilization without inflammatory related complication is desired. MethodsIn this randomized controlled trial study 48 adult males were enrolled who experienced elective inguinal hernia repair under spinal anesthesia. Subjects were categorized in 2 groups with equal 24 members in each including patients received local anesthetic (2 mg kg−1 of bupivacaine 0.5%) in addition to spinal anesthesia and controlled who had spinal anesthetic with local placebo injection. Plasma cortisol and prolactin concentration were obtained 1 h before and 3 h after operation. To evaluate severity of postoperative pain the visual analogue scale(VAS) was applied. We also measured the total dosage of analgesic requirement among patients. ResultsData showed that spinal anesthesia alone was followed by increasing plasma concentration of either cortisol or prolactin postoperatively (P < 0.01). Findings according to investigate severity of pain implied on that local anesthesia could make more postoperative comfort for patients with inguinal herniorrhaphy(P < 0.001). Therefore, analgesic requirement in patients who were equipped by additional local anesthesia also decreased(P < 0.001). ConclusionsWe concluded that adding local anesthetic to basic spinal anesthesia during inguinal herniorrhaphy could induce to either lower stress hormones plasma concentration or decrease pain and need for analgesic postoperatively.

Comparative Assessment of Thermotolerance in Dorper and Second-Cross (Poll Dorset/Merino × Border Leicester) Lambs.

Simple SummarySelection of animal breeds that are adapted to extreme climatic conditions may help to sustain livestock production in the face of climate change. We measured the thermotolerance of 4–5-month-old Dorper and second-cross lambs (Poll Dorset × (Border Leicester × Merino)) by assessing feed intake, physiological, blood biochemical and prolactin responses. Heat stress reduced feed intake only in second-cross lambs but not in Dorpers. As expected, heat stress also increased water intake, respiration rate, rectal temperature, and skin temperature in both genotypes, but to a lesser extent in Dorpers. The comparatively lower influence of heat stress on thermotolerance indices in Dorper indicates adaptability of this breed to heat challenge.The objective of this study was to compare the thermotolerance of second-cross (SC; Poll Dorset × Merino × Border Leicester) and Dorper lambs. Dorper and SC lambs (4–5 months of age) were subjected to cyclic heat stress (HS) (28–40 °C). The temperature was increased to 38–40 °C between 800 and 1700 h daily and maintained at 28 °C for the remainder of the day (30–60% relative humidity (RH)) in climatic chambers for 2 weeks (n = 12/group), with controls maintained in a thermoneutral (TN) (18–21 °C, 40–50% RH) environment (n = 12/group). Basal respiration rate (RR), rectal temperature (RT) and skin temperature (ST) were higher (p < 0.01) in SC lambs than in Dorpers. HS increased RR, RT and ST (p < 0.01) in both genotypes, but the levels reached during HS were lower (p < 0.01) in Dorpers. HS increased (p < 0.01) water intake to a greater extent in SC lambs, while feed intake was reduced (p < 0.05) by HS in SC lambs but not in Dorpers. HS increased (p < 0.01) blood urea nitrogen and creatinine in SC lambs only. Plasma non-esterified fatty acid concentrations were reduced (p < 0.05) by HS in SC lambs but increased (p < 0.05) in Dorpers. There was no effect of HS on pO2, cHCO3− and cSO2, but higher (p < 0.01) blood pH and lower (p < 0.01) pCO2 were recorded under HS in both genotypes. Blood electrolytes and base excess were reduced (p < 0.01) under HS, while a genotype difference (p < 0.05) was only observed in blood K+ and hemoglobin concentrations. Basal plasma prolactin concentrations were lower (p < 0.01) in Dorpers but were elevated at a similar level during HS (p < 0.01) in both genotypes. Dorper lambs are more resilient to HS than SC lambs. Future research should focus on confirming whether the better heat tolerance of Dorpers is translated to better returns in terms of growth performance and carcass traits over the summer months.

Feeding yearling Angus bulls low-level ergot daily for 9 weeks decreased serum prolactin concentrations and had subtle effects on sperm end points

Our objective was to determine whether feeding yearling bulls with the higher recommended Canadian limit of ergot alkaloids (∼3 mg/kg dry matter intake, DMI) would affect sperm characteristics and plasma prolactin concentrations. Aberdeen Angus bulls (12–13 mo old, n = 7/group) allocated by blocking for sperm concentration and body weight, were fed placebo or ergot alkaloids in gelatin capsules (60 μg/kg body weight daily, 3.4 mg/kg of DMI) for 9 wk. Semen samples were collected weekly by electroejaculation and examined with a computer assisted semen analyzer (CASA) and flow cytometry, for the intervals 5 wk before (Pre-exposure period), 9 wk during (Exposure period) and 9 wk after (Post-exposure period) treatment. Weekly plasma samples were analyzed for prolactin by radioimmunoassay. Plasma prolactin concentrations decreased markedly (mean ± SEM, 16.74 ± 3.70 in Exposure and 33.42 ± 3.08 ng/mL in Post-Exposure periods; P < 0.01) compared to Control (67.54 ± 21.47 and 42.59 ± 15.06 ng/mL). Treatment did not affect (P ≥ 0.17) body weight gain, sperm concentration, sperm count/ejaculate, motility or percent live sperm. Averaged over the exposure and post-exposure durations, the scrotal circumference was smaller (P = 0.02) by 2.7% in the Ergot group. Progressive motility remained unchanged from 59.92 ± 2.31% in Exposure to 59.61 ± 2.59% in Post-Exposure periods, compared to marked increase in Control (61.42 ± 1.60% to 67.52 ± 1.47%; P = 0.02). Straight-line sperm velocity decreased (−3.15 ± 1.53 μm/s) from exposure to post-exposure periods in Ergot group (P = 0.04) versus an increase (2.96 ± 2.17 μm/s) in Control. Midpiece defects decreased from Exposure to Post-exposure periods in Control group but remained unchanged in Ergot group (trt∗age, P < 0.01). Ergot feeding resulted in a smaller proportion of sperm with medium mitochondrial potential (Ergot: 22.65 ± 0.98%, Control: 24.35 ± 1.05%, P = 0.04). In conclusion, feeding ergot at Canadian permissible limit for 9-wk resulted in a 4-fold decrease in plasma prolactin concentrations. Semen end points were not significantly affected, although there were subtle effects on progressive motility, midpiece defects and mitochondrial membrane potential. Clinical relevance of observed changes requires further evaluation. Results supported our hypothesis that prolonged low-level ergot will adversely affect plasma prolactin. However, semen parameters were partially affected, supporting similar work on fescue toxicosis.

The effect of photoperiod and melatonin on plasma prolactin concentrations in female guanaco (Lama guanicoe) in captivity.

The present study examined the effects of different photoperiods and melatonin treatment on plasma prolactin concentrations in guanacos, a South American camelid, in captivity. Fourteen adult female guanacos, not gestating or lactating and isolated from males, were studied. The control group was exposed to natural daylight, during short days (N=7, 10L:14D) and long days (N=7, 16L:8D). The treatment group (N=7, 10L:14D) received melatonin implants every 23days for 6weeks during long days. Blood samples were taken at intervals of 1week for 3weeks, starting the third week of treatment. Prolactin concentrations were measured using competitive ELISA. Plasma concentrations of prolactin in non-lactating female guanacos have seasonal changes, with a higher concentration (p<.001) in short days (3.50±2.24ng/ml) than long days (1.10±0.91ng/ml). Melatonin treatment significantly decreases (p<.05) plasma concentrations of prolactin on the 21st day after the treatment. These findings are the first report of an endogenous circannual rhythm of plasma prolactin concentration and the action of melatonin treatment on prolactin secretion in this wild camelid.

Suppression of prolactin and reduction of milk secretion by effect of cabergoline in lactating dairy ewes

The effects of cabergoline, an ergot derivative and dopamine receptor agonist, were investigated in 30 ewes of 2 dairy breeds (Manchega; MN, n = 15; Lacaune; LC, n = 15). Ewes were in a similar late-lactation stage, but differed in milk yield according to breed (MN vs. LC, 1.02 ± 0.03 vs. 2.27 ± 0.05 kg/d). Treatments consisted of a single intramuscular injection of cabergoline at different doses per ewe. Cabergoline doses (per ewe) were: low (0.56 mg), high (1.12 mg), and control (CON; 0 mg; 1 mL of saline). Milk yield was recorded daily (d -14 to 25), milk and blood were sampled, and udder traits were measured from d -2 to 14 after injection. No local reaction at the injection site, nor behavior and metabolic indicators of the ewes were detected after the cabergoline injection, but milk yield fell rapidly in both breeds (MN vs. LC, -54% vs. -27%) when compared with CON ewes. Cabergoline effects progressively disappeared after d 5, and no milk yield differences between treatments were detected from d 8 to 25 after injection. Milk fat and protein contents increased similarly (22% and 23%; respectively) in both breeds and at both cabergoline doses until d 5, and the effects disappeared thereafter. Plasma prolactin (PRL) decreased dramatically in the low- and high-treated ewes the day after injection when compared with the CON ewes, and reached values below the detection limit of the assay between d 1 and 5, increasing similarly thereafter. On d 14, PRL values were 58% greater in the low- and high-treated than in the CON ewes, showing that PRL concentrations rebounded when the cabergoline effects ceased. Total udder volume correlated with milk accumulated in the udder (r = 0.77) of all groups of ewes throughout the experiment, suggesting its use as a noninvasive method for the estimation of milk stored in the udder. Udder volume was similar for the low and high ewes, but both values were lower than those of the CON ewes from d 1 to 14 after injection. No other effects on udder size were detected. Cabergoline dramatically inhibited PRL secretion and decreased milk yield and udder volume of lactating dairy ewes. The low dose of cabergoline was as effective as the high dose in the 2 breeds of dairy ewes. These results suggest the use of cabergoline to facilitate the decrease of milk production in dairy ewes (e.g., dry-off, illness care), although further research in pregnant dairy ewes and during the following lactation is still needed.

Transcript Abundances of the Prolactin Receptor, the Leptin Receptor and their Major Suppressor in the Sheep Mammary Gland During Pregnancy and Lactation

Abstract This study aimed to expand the knowledge of the interactions between prolactin (PRL) and leptin in the ovine mammary gland during pregnancy and lactation; we examined the mRNA expression of prolactin receptor (PRLR), the long form of the leptin receptor (LRb) and suppressor of cytokine signaling (SOCS)-3 in mammary gland biopsies collected on days 60, 90 and 120 of pregnancy and on days 30, 60 and 90 of lactation (n = 6 for each time point), along with the plasma PRL and leptin concentrations. The PRL concentrations were stable throughout pregnancy and increased during lactation. The plasma leptin concentrations were comparable among nonpregnant, early-pregnant, late-pregnant and lactating ewes, but this metric peaked during mid-pregnancy. Expression of PRLR and SOCS-3 in the mammary gland fluctuated during the transition from pregnancy to lactation, and differences in LRb expression occurred during the late stages of lactation. The LRb transcript abundance was approximately 31 times higher in ewes on day 60 of lactation than in early-lactating ewes. Expression of SOCS-3 mRNA in biopsies gradually decreased over the course of pregnancy and reached a minimum value during late pregnancy. After lambing, the transcript level of SOCS-3 increased and peaked on day 60 of lactation. During pregnancy, the plasma PRL concentration positively correlated with the abundances of PRLR (r = 0.971, P&lt;0.01) and SOCS-3 (r = 0.818, P&lt;0.05). Positive correlations were also observed between the transcript abundances of SOCS-3 and LRb (r = 0.854, P&lt;0.05). The variations observed in the plasma PRL and leptin concentrations and the changes in expression of key leptin and PRL signal transduction pathway components, such as PRLR, LRb and SOCS-3, indicate that the efficacies of both hormone actions are modulated in a multilevel manner throughout pregnancy and lactation. These interactions may regulate the ability of the mammary gland to respond to current energy requirements and challenges, thus affecting milk yield and lactation duration.

Paeoniflorin ameliorates antipsychotic-induced hyperprolactinemia in rats by attenuating impairment of the dopamine D2 receptor and TGF-β1 signaling pathways in the hypothalamus and pituitary

Ethnopharmacological relevancePaeoniflorin, a prominent component in some Chinese formulas for hyperprolactinemia-associated disorders, has been found to inhibit prolactin secretion in prolactinoma cells. AimTo examine the efficacy of paeoniflorin on hyperprolactinemia and the underlying mechanisms of action. Materials and methodsHyperprolactinemia in female rats was generated by administration of olanzapine (5 mg/kg, by a gavage method, once daily, × 13 weeks). The rats were co-treated with paeoniflorin (10 and 50 mg/kg). Prolactin and TGF-β1 concentrations were detected by ELISA. Protein expression was determined by Western blot. The effect in MMQ cells was also examined. ResultsPaeoniflorin inhibited olanzapine-induced increases in plasma prolactin concentration and prolactin protein overexpression in the pituitary and hypothalamus of rats. Further, paeoniflorin restored olanzapine-induced downregulation of pituitary and hypothalamic dopamine D2 receptor (D2R) protein expression. More importantly, paeoniflorin attenuated olanzapine-suppressed protein expression of transforming growth factor (TGF)-β1 and its downstream genes, type II TGF-β receptor, type I TGF-β receptor and phosphorylated SMAD3 in the tissues. However, paeoniflorin did not affect plasma TGF-β1 concentration and hepatic TGF-β1 protein expression. In accord, olanzapine-induced increase in prolactin concentration, upregulation of prolactin protein expression, and downregulation of protein expression of the D2R and TGF-β1 signals in MMQ cells were attenuated. ConclusionsThis study demonstrates that paeoniflorin ameliorates olanzapine-induced hyperprolactinemia in rats by attenuating impairment of the D2R and TGF-β1 signaling pathways in the hypothalamus and pituitary. Our findings may provide evidence to support the use of paeoniflorin-contained Chinese herbs and formulas for hyperprolactinemia and its associated disorders.