Prolactin Response Research Articles

Acute salinity challenges in Mozambique and Nile tilapia: Differential responses of plasma prolactin, growth hormone and branchial expression of ion transporters

The responses of Mozambique and Nile tilapia acclimated to fresh water (FW) and brackish water (BW; 17‰) were compared following acute salinity challenges. In both species, plasma osmolality increased to above 450 mOsm by 2 h after transfer from FW to seawater (SW); these increases in osmolality were accompanied by unexpected increases in plasma prolactin (PRL). Likewise, PRL receptor gene expression in the gill also increased in both species. In Nile tilapia, hyperosmotic transfers (FW to BW and SW) resulted in increased plasma growth hormone (GH) and in branchial GH receptor gene expression, responses that were absent in Mozambique tilapia. Branchial gene expression of osmotic stress transcription factor 1 (OSTF1) increased in both species following transfer from FW to SW, whereas transfer from BW to SW induced OSTF1 expression only in the Nile tilapia. Branchial expression of Na +/Cl − cotransporter was higher in FW in both species than in BW. Branchial gene expression of Na +/K +/2Cl − cotransporter (NKCC) increased after transfer from BW to SW in Mozambique tilapia, whereas expression was reduced in the Nile tilapia following the same transfer. The difference in the SW adaptability of these species may be related to a limited capacity of Nile tilapia to up-regulate NKCC gene expression, which is likely to be an essential component in the recruitment of SW-type chloride cells. The differential responses of GH and OSTF1 may also be associated with the disparate SW adaptability of these two tilapiine species.

Characteristics of prolactin-releasing response to salsolinol in vivo in cattle

The aims of the present study were to clarify the effect of salsolinol (SAL), a dopamine (DA)-derived endogenous compound, on the secretion of prolactin (PRL) in cattle. The experiments were performed from April to June using calves and cows. A single intravenous (i.v.) injection of SAL (5 mg/kg body weight [BW]) or sulpiride (a DA receptor antagonist, 0.1 mg/kg BW) significantly stimulated the release of PRL in male and female calves ( P < 0.05), though the response to SAL was smaller than that to sulpiride. The secretory pattern of PRL in response to SAL or sulpiride in female calves resembled that in male calves. A single i.v. injection of SAL or sulpiride significantly stimulated the release of PRL in cows ( P < 0.05). There was no significant difference in the PRL-releasing response between the SAL- and sulpiride-injected groups in cows. A single intracerebroventricular injection of SAL (10 mg/head) also significantly stimulated the release of PRL in castrated calves ( P < 0.05). These results show that SAL is involved in the regulatory process for the secretion of PRL, not only in male and female calves, but also in cows. The results also suggest that the potency of the PRL-releasing response to SAL differs with the physiological status of cattle.

Prolactin and LH responses to estradiol cypionate followed by sulpiride or domperidone administration in winter

Prolactin and LH responses to estradiol cypionate followed by sulpiride or domperidone administration in winter

Improvement in antipsychotic-induced hyperprolactinemia with the addition of aripiprazole in schizophrenic patients

Purpose: Hyperprolactinemia, a common adverse effect of antipsychotics, frequently impacts patients' quality of life. Aripiprazole is a potent dopamine D2 receptor partial agonist and rarely increases the serum prolactin concentration. The authors investigated the effect of aripiprazole coadministration on antipsychotic-induced hyperprolactinemia and associated symptoms in patients with schizophrenia.Method: The subjects were 9 patients (8 females, 1 male) with hyperprolactinemia induced by risperidone, olanzapine, haloperidol, zotepine, bromperidol, levomepromazine, and quetiapine; 6 of the females had oligomenorrhea and 2 amenorrhea, and the male had erectile dysfunction. All of the patients received concomitant aripiprazole for more than 8 weeks at a mean dose (range) of 7.7 (3-18) mg/day. The doses of all other medications, including the hyperprolactinemia-inducing antipsychotics, remained fixed throughout the study period.Results: The mean serum concentration (range) of prolactin during aripiprazole coadministration (29.9 (9.8-53) ng/ml) was significantly (p=0.008) lower than that before aripiprazole coadministration (81.1(27-153) ng/ml). The associated symptoms were improved in 4 females (regularized or regained menstruation) and the male (normalized erectile function), while no changes were observed in the other clinical symptoms of schizophrenia.Discussion: The results of the present study suggest that even small doses of coadministered aripiprazole effectively limit excessive prolactin response to antipsychotics without interfering with the benefits of existing prescriptions.

Blunted opiate modulation of prolactin response in smoking men and women

Endogenous opioids are integral in modulating drug reward, but it is believed that these may act through several mechanisms including hypothalamic-pituitary-adrenocortical (HPA) and dopamine pathways. This study was developed to examine how nicotine dependence alters endogenous opioid regulation of prolactin response, a peripheral marker of dopaminergic activity. Smokers and nonsmokers completed two sessions during which placebo or 50 mg of naltrexone was administered, using a double-blind, counterbalanced design. Blood samples and mood measures were obtained during a resting absorption period, after exposure to two noxious stimuli (cold pressor and thermal pain), and during an extended recovery period. Opioid blockade increased prolactin response, indicating an inhibitory effect of the endogenous opioid system on prolactin, possibly mediated by reduced stimulatory effects of dopamine on this hormone. These responses were attenuated in smokers relative to nonsmokers. There was also a gender disparity in prolactin response, with women showing a stronger response to endogenous opioid modification than men regardless of smoking status. The attenuated effects of opioid blockade may reflect dysregulated opiodergic and dopaminergic effects. Results extend previous reports showing blunted opioid regulation of the HPA response in dependent smokers.

Impact of Prolonged High Altitude Exposure on Plasma Prolactin in Men: Effect of Age and Ethnicity

Hormonal changes during high-altitude (HA) exposure are important for normal adaptation to the new environment in lowlanders. Prolactin (PRL), a stress hormone, is involved in the regulation of fertility, immune response, osmotic balance, and angiogenesis. However, little is known about the effect of age and ethnicity on plasma PRL changes in men during prolonged HA exposure. The aim of this research was to examine possible age and ethnic variation in plasma PRL levels in men after 3 to 4 weeks of stay at HA (approximately 4500 m) in the Indian population. Lowlanders of Rajput (n = 49), Gorkha (n = 70), and South Indian (n = 40) ethnicities were studied at sea level (SL). They were taken to an altitude of approximately 4500 m where they stayed for 3 to 4 weeks. Another group of HA natives (Ladakhi, n = 65) was studied at similar altitude. Subjects were between 20 to 50 yr of age. At HA, plasma PRL showed a decrease in Rajputs and Gorkhas (p < 0.05), whereas there was an increase (p < 0.05) in South Indians when compared to SL. There was no age variation in PRL. PRL levels in HA natives were within the SL normal range observed in lowlanders. PRL response to HA stress in lowlanders is influenced by ethnicity. The exact cause for such differences in PRL secretion under HA stress is not clearly known. Further studies on the physiological regulation of PRL at HA are needed.

Effect of Ghrelin and Thyrotropin-releasing Hormone on Prolactin Secretion in Normal Women

It is known that ghrelin stimulates the secretion of prolactin in women. The aim of this study was to examine the effect of exogenous thyrotropin-releasing hormone (TRH) on ghrelin-induced prolactin release. Ten healthy normally cycling women were studied in four menstrual cycles. The women were injected intravenously in late follicular phase (follicle size 16-17 mm) with a single dose of normal saline (cycle 1), ghrelin (1 microg/kg) (cycle 2), thyrotropin-releasing hormone (200 microg) (cycle 3), and ghrelin plus thyrotropin-releasing hormone (cycle 4). Blood samples in relation to saline or drugs injection (time 0) were taken at -15, 0, 15, 30, 45, 60, 75, 90, and 120 min. The prolactin and growth hormone responses were assessed. After ghrelin administration (cycles 2 and 4), plasma ghrelin, serum prolactin, and growth hormone levels increased rapidly, peaking at 15-30 min (p<0.001). The injection of thyrotropin-releasing hormone (cycle 3) stimulated prolactin secretion markedly (p<0.001), but reduced growth hormone levels significantly (p<0.05). Ghrelin induced a smaller prolactin increase than thyrotropin-releasing hormone (p<0.05). The combination of ghrelin and thyrotropin-releasing hormone induced a similar increase in prolactin levels as with thyrotropin-releasing hormone alone. No changes in growth hormone and prolactin levels were seen after saline injection. These results demonstrate that the stimulating effect of ghrelin on prolactin secretion is not additive with that of thyrotropin-releasing hormone.

Facteurs prédictifs de la survenue du stress post-traumatique chez des individus ayant vécu deux évènements de vie majeurs (tremblement de terre et terrorisme en Algérie) : réponse corticotrope et prolactinique à une faible dose de dexaméthasone (0,5 mg)

This article is to give an outline on some scientific experiments on the effects of the posttraumatic stress disorder (psychic factors) on the variations neuroendocriniennes (adrenal and prolactinic). The prolactin and cortisol responses to dexamethasone (0.5 mg) were studied in masculin subject posttraumatic stress disorder (PTSD) ( n = 10), normal controls ( n = 18) and non PTSD subjects ( n = 10), in order to better determine these interactions. Both the two groups of subjects which lived events of everyday life extremely stressing (PTSD and not PTSD) showed an enhanced cortisol suppression in response to dexamethasone than the normal subjects. In contrast, only the PTSD showed an hypersuppression of cortisol to the dexamethasone. These findings suggest that the prolactin response to dexamethasone in the non PTSD subjects can reflect a predictive indicator of occurred of the PTSD.

Inferior petrosal sinus ACTH and prolactin responses to CRH in ACTH-dependent Cushing’s syndrome: a single centre experience from the United Kingdom

Inferior petrosal sinus sampling (IPSS) of ACTH with CRH stimulation helps distinguish pituitary ACTH-dependent Cushing's syndrome from the ectopic ACTH syndrome (EAS). The usefulness of the paradoxical response of other pituitary hormones including prolactin to CRH remains controversial. Data from 33 IPSS procedures carried out at the Walton Centre for Neurology and Neurosurgery in Liverpool were analyzed. Patients were selected for this procedure if they had been diagnosed with ACTH dependent Cushing's syndrome and the majority had no obvious pituitary adenoma on Magnetic Resonance Imaging. Satisfactory simultaneous bilateral catheterization was accomplished in 23/33 (success rate 70%). The diagnostic sensitivity of a basal central/peripheral ACTH ratio >2.0 and >3 post-CRH was 94%. In two patients with subsequently confirmed EAS the maximal central/peripheral ACTH ratio was <2.0 on basal samples and did not change following CRH. The maximal central/peripheral prolactin ratio was noted at 5 min post-CRH, coinciding with the maximal central/peripheral ACTH ratio. The intersinus gradient (ISG) of ACTH was paralleled by a consistent ISG of prolactin and in 7 out of 9 patients (with successful bilateral IPSS and unilateral adenomas) the ISG of prolactin correctly lateralized the microadenoma whereas the ISG of ACTH correctly lateralized in 8 out of 9 patients. Neither of the patients with EAS achieved a central/peripheral prolactin ratio >2 in the basal state and >3 post-CRH. Bilateral catheterization of inferior petrosal sinuses can be successful in up to 70% of cases. Prolactin measurements do not have superior lateralizing capability compared with ACTH but may be useful in the differential diagnosis of pituitary-driven from EAS.

What Factors Drive Prolactin and Corticosterone Responses to Stress in a Long‐Lived Bird Species (Snow PetrelPagodroma nivea)?

Life-history theory predicts that individuals should adapt their parental investment to the costs and benefits of the current reproductive effort. This could be achieved by modulating the hormonal stress response, which may shift energy investment away from reproduction and redirect it toward survival. In birds, this stress response consists of a release of corticosterone that may be accompanied by a decrease in circulating prolactin, a hormone involved in the regulation of parental care. We lack data on the modulation of the prolactin stress response. In this study, we tested the hypothesis that individuals should modulate their prolactin stress response according to the fitness value of the current reproductive effort relative to the fitness value of future reproduction. Specifically, we examined the influence of breeding status (failed breeders vs. incubating birds) and body condition on prolactin and corticosterone stress responses in a long-lived species, the snow petrel Pagodroma nivea. When facing stressors, incubating birds had higher prolactin levels than failed breeders. However, we found no effect of body condition on the prolactin stress response. The corticosterone stress response was modulated according to body condition but was not affected by breeding status. We also performed an experiment using injections of adrenocorticotropic hormone (ACTH) and found that the modulation of the corticosterone stress response was probably associated with a reduction in ACTH release by the pituitary and a decrease in adrenal sensitivity to ACTH. In addition, we examined whether prolactin and corticosterone secretion were functionally linked. We found that these two hormonal stress responses were not correlated. Moreover, injection of ACTH did not affect prolactin levels, demonstrating that short-term variations in prolactin levels are not governed directly or indirectly by ACTH release. Thus, we suggest that the corticosterone and prolactin responses to short-term stressors are independent and may therefore mediate some specific components of parental investment in breeding birds. With mounting evidence, we suggest that examining both corticosterone and prolactin stress responses could be relevant to parental investment in vertebrates.

Growth hormone and prolactin response to ghrelin during the normal menstrual cycle

It has been suggested that exogenous oestradiol augments ghrelin-induced growth hormone (GH) secretion in postmenopausal women. Whether endogenous oestrogens exert a similar effect during the normal menstrual cycle is not known. The aim of this study was to test the hypothesis that physiological changes in ovarian steroids during the normal menstrual cycle modulate GH and prolactin (PRL) response to ghrelin. Healthy women were studied in three phases of the normal menstrual cycle. Ten healthy normally cycling women. A single dose of ghrelin (1 microg/kg) was administered intravenously in the early and late follicular phases and in the mid-luteal phase of the cycle. Saline was injected in the preceding cycle. Blood samples were taken before ghrelin or saline injection (time 0) and also at -15, 15, 30, 45, 60, 75, 90 and 120 min. The GH and PRL responses were assessed. Serum oestradiol and progesterone concentrations showed the variations of a normal menstrual cycle. After ghrelin administration, in the three phases of the cycle, plasma ghrelin and serum GH and PRL levels increased rapidly, peaking at 30 min and declining gradually thereafter (P < 0.001). There were no significant differences in the hormone levels between the three phases at all time points. No changes in GH and PRL levels were seen after saline injection. These results demonstrate that GH and PRL responses to ghrelin do not change across the menstrual cycle. It is suggested that the action of ghrelin on the pituitary somatotrophs is modulated differentially by endogenous and exogenous ovarian steroids.

Pregnancy alters prolactin and cytokine responses to stress in mice

Pregnancy alters prolactin and cytokine responses to stress in mice

Abnormal neuroendocrine response to clomipramine in hereditary affective psychosis

Blunting of prolactin response after serotonergic stimulation during a major depressive episode has been described by several investigators. In this study, the neuroendocrine responses to clomipramine were assessed in remitted patients suffering from hereditary depression. Twenty remitted patients from 11 large families with multigenerational, multiple cases of major affective disorder (bipolar disorder n=15, recurrent depression n=5, according DSM-IV) and 12 healthy relatives were investigated. After intravenous application of 12.5 mg of the serotonin re-uptake inhibitor clomipramine, serum prolactin and cortisol levels were analysed. Patients and comparison group did not differ significantly with respect to age, baseline prolactin and cortisol concentrations. A gender effect was found in an exploratory analysis for prolactin but not for cortisol and therefore the data for prolactin were analysed separately. After clomipramine infusion, the increase of cortisol was significantly lower in patients than in the comparison group (P=.046). For prolactin, this effect could be found in the male (P=.012) as well as in the female (P=.007) subsample. These results suggest that blunted prolactin and cortisol responses to serotonergic stimulation are characteristic for remitted depressive patients with previous episodes of major affective disorders.

Corticosterone and prolactin responses to repeated handling and transfer of male rats.

The changes of plasma corticosterone and prolactin levels have been studied in rats after single, repeated or cross exposition to the moderate stressors: handling and transfer. The diminution of corticosterone and prolactin response has been found after repeated handling, but not after repeated transfer. The corticosterone level was significantly elevated in both cross-transfer and cross-handling groups and plasma prolactin level was significantly higher in the cross-handling animals. Both hormones manifested a parallel reaction to stress, prolactin being more difficult to obtain diminution of the reaction, corticosterone being more adaptable to repeated stress. It is concluded that the cross-adaptation between used stressful stimuli apparently could not be demonstrated, but, in contrast, the organism adapted to one stimulus possesses a greater corticosterone and prolactin reaction when being exposed to the new stimuli.

Dissociation of prolactin and LH release responses after stimulation within the preoptic-suprachiasmatic region in male rats.

The relative efficiency of unilateral electrical stimuli applied within the preoptic-suprachiasmatic region (POA-Sch) to induce the release of prolactin and/or LH was studied in male rats under pentobarbital anesthesia. It was observed that unilateral stimulation with 10 Hz, 1.0 msec width pulses applied in the ventral half of the POA-Sch resulted primarily in the release of prolactin rather than LH. Fifty Hz stimuli applied at this same locus resulted also in LH release. It is concluded that the probability to dissociate the induced release of prolactin and LH from the anterior pituitary in male rats after stimulation from a given locus within the ventral POA-Sch is significantly affected by the characteristics of the applied stimulus.

Decrease of prolactin response to TRH during ageing in women.

The response of prolactin after thyreoliberin decreased with ageing. The role of estrogen secretion in this phenomenon is discussed.

Plasma Cortisol and Prolactin Response to Insulin-Induced Hypoglycemia in Neurosis

Prolactin (PRL) and plasma cortisol response to insulin induced hypoglycemia were studied in 14 patients with various somatic and vegetative complaints of neurotic character and in 12 controls. In all examined subjects glucose level fell below 50% of basal values and below 2.2 mmol/l. Significant PRL and plasma cortisol response were present in all controls. Plasma cortisol increase in control group was at least 1.5 fold higher than basal values and the difference between basal concentrations and highest values after stimulation was at least 0.25 mumol. Individual peak of PRL values in group of controls was 1.8-10 fold greater than basal levels. In the group of 14 patients in 11 cases no PRL response to challenge was found and in 4 cases also plasma cortisol response was blunted. In two patients extremely exaggerated PRL reaction was found. Different PRL responses to insulin-induced hypoglycemia are probably a manifestation of different types of neurotransmitter metabolism breakdown.

Prolactin and thyrotropin response to thyrotropin-releasing-hormone in adolescent females with insulin-treated diabetes mellitus.

Prolactin and thyrotropin response to TRH and basal gonadotropins levels in blood were investigated in insulin-treated adolescent females with regular menstruation cycles (Group I) and menstruation disturbances (Group II) compared with control, healthy girls. No significant differences were found in TSH secretion after TRH administration and basal LH, FSH levels between the observed groups. Blood basal PRL levels were significantly lower in young females in Group II, and a highly increased mobilization of PRL secretion (delta % PRL)--masked hyperprolactinaemia--in all of the groups of diabetic girls was revealed. Cytological examination of vaginal smears confirmed hypoestrogenic status of girls from Group II compared with Group I and the control group.

Serum Aldosterone Response to Metoclopramide in Normal Subjects and Acromegalic Patients

The acute effects of metoclopramide on aldosterone and prolactin levels were studied in 11 normal subjects, 8 normotensive and 8 hypertensive acromegalics. Metoclopramide (10 mg i.v.) induced a similar serum aldosterone increase in normal subjects and normotensive acromegalics. Hypertensive acromegalics showed elevated basal serum aldosterone level and blunted aldosterone response to metoclopramide. The prolactin response to metoclopramide was blunted in acromegalics in comparison with normal subjects but the difference was statistically significant only in hypertensive patients. The blunted aldosterone and prolactin responses to metoclopramide in hypertensive acromegalics suggest that there is a dopamine deficiency at central and adrenal level in these patients.

Prolactin Secretion in Myotonic Dystrophy

In order to evaluate prolactin secretion in females with myotonic dystrophy (MD) prolactin responses to TRH, metoclopramide and bromocriptine were studied in 13 women with myotonic dystrophy (10 normoprolactinaemic and 3 hyperprolactinaemic) and 8 healthy women. Following TRH administration mean maximal net increase was significantly higher in a group of normoprolactinaemic patients with MD in comparison to controls (p less than 0.05). In three patients with increased basal prolactin levels an exaggerated prolactin response to TRH has been observed. Normal prolactin response in a group of normoprolactinaemic as well as in hyperprolactinaemic patients have been observed following metoclopramide bolus injection. Following bromocriptine administration, maximal net decrease in prolactin levels has been found to be greater in normoprolactinaemic patients compared to healthy subjects, although the difference was statistically insignificant. The suppressive action of bromocriptine was more pronounced in patients with hyperprolactinaemia. Those results showed that there is some derangement in prolactin secretion in myotonic dystrophy leading to increased prolactin levels in some patients. Although the mechanism of this derangement has not been clarified yet it seems that it is not mediated via dopaminergic receptors.