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Ropinirole (4-[2-(dipropylamino)ethyl]-2-indolinone monohydrochloride) a nonergoline dopamine receptor agonist with high affinity for native dopamine D(2)-like receptors in human caudate tissue, was tested with respect to the stimulation of postsynaptic brain dopamine receptors in standard preclinical models of Parkinson's disease. Additionally, in these animal models the antiparkinsonian activity of ropinirole was compared to that of bromocriptine. The ED(50)s (95% confidence limits) of ropinirole and bromocriptine on the turning behavior in 6-OHDA-lesioned rats were 20.17 mg/kg (14.27-26.88 mg/kg) and 11.99 mg/kg (9.37-14.17 mg/kg), respectively. The ED(50)s (95% confidence limits) of ropinirole and bromocriptine on the catalepsy induced by reserpine were 18.55 mg/kg (15.29-22.99 mg/kg) and 12.56 mg/kg (10.25-14.64 mg/kg), respectively. Ropinirole and bromocriptine had no effect on the tremors induced by oxotremorine in mice, whereas atropine markedly suppressed the tremors. The ED(50)s (95% confidence limits) of ropinirole and bromocriptine on the tremors in VMT-lesioned monkeys were 0.18 mg/kg (0.12-0.29 mg/kg) and 2.63 mg/kg (1.06-6.45 mg/kg), respectively. In rodent parkinsonian models, bromocriptine was more potent than ropinirole; however, in the nonhuman primate parkinsonian model, ropinirole was a more potent inhibitor of parkinsonian activity than bromocriptine. This study suggests that ropinirole is a dopamine D(2)-like receptor agonistic drug of potential use in the treatment of Parkinson's disease.
Glycoprotein-secreting pituitary tumors are uncommon. With increased awareness that pituitary tumors may secrete FSH, LH, TSH, and the alpha-subunit, either as a sole product or in any combination, these tumors are more likely to be recognized. The standard therapy is surgical resection and, possibly, postoperative radiotherapy for residual tumor mass or persistent hormonal secretion. We report a patient with a FSH- and alpha-subunit-secreting tumor who refused surgery and was treated with the dopamine agonist bromocriptine as primary therapy. Bromocriptine treatment resulted in reduction of serum FSH and alpha-subunit levels to normal, improvement of visual field defects, and improvement in hypogonadism despite lack of demonstrable change in tumor size, as assessed by computed tomographic scan. Chromatographic analysis of the serum revealed distinct peaks corresponding to those of labeled FSH and alpha-subunit. The clinical and biochemical responses in this patient suggest that some glycoprotein-secreting tumors may be responsive to dopamine agonist therapy.
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This study investigated whether photoperiod-induced changes in circulating prolactin levels, which have been observed in the Djungarian hamster ( Yellon and Goldman, '83; Duncan and Goldman, ' 83a ), might be involved in seasonal pelage color changes in this species. Injection of ovine prolactin (100 micrograms/day) inhibited the short photoperiod-induced winter molt. This finding indicated that the suppression of endogenous prolactin levels normally occurring in short photoperiod-housed hamsters (Duncan and Goldman, ' 83a ) may induce the winter molt. Suppression of prolactin secretion with bromoergocryptine (200 micrograms/day) strongly inhibited the spring molt, while concomitant treatment with ovine prolactin (100 micrograms/day) overcame this effect of bromoergocryptine. Injection of bromoergocryptine (200 micrograms/day) stimulated the winter molt in castrated hamsters housed in long photoperiod; concomitant injection of prolactin (100 micrograms/day) reversed this effect as well. These findings strongly suggested that an increase in endogenous prolactin levels may be necessary for the development and maintenance of the summer pelage.
A 59-year-old man, who was diagnosed as having Parkinson's disease and depression seven years ago and was on oral antiparkinsonian agents, antianxiety agents, and antidepressants, developed a high fever, disturbed consciousness, and marked muscle rigidity after discontinuation of etizolam and amitriptyline. He was admitted to a nearby hospital. Hypothyroidism had been noted two months before admission. Marked muscle rigidity and increased serum CK were observed. Since discontinuation of benzodiazepine has been known to rarely trigger a neuroleptic malignant syndrome (NMS), he was diagnosed as having NMS. After receiving dantrolene and bromocriptine, these symptoms temporarily improved but he again developed consciousness disturbance, and convulsive seizures associated with an elevated serum CK. He was transferred to our hospital. On admission, the CK level was normal at 168 IU/l, while free T4 was 0.6 ng/dl (normal range, 0.9-2.3) and TSH was 108.7 mU/ml (normal range, 0.2-4.2) in serum, indicating the presence of primary hypothyroidism. As an increase in thyroid hormone dosage improved the thyroid function to normal level, his disturbed consciousness and muscle rigidity gradually improved. Convulsive seizure and recurrence of NMS in a short interval are unusual in neuroleptic malignant syndrome. In this patient, hypothyroidism may have contributed to the development of malignant syndrome through metabolic changes of the central dopaminergic system, and discontinuation of etizolam, a kind of benzodiazepine, may have triggered NMS, since there has not been reported that discontinuation of antidepressants including amitriptyline triggers NMS.
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Although it is well established that PRL is present in the maternal serum, fetal serum, and amniotic fluid during human pregnancy, the precise interrelationship among those three compartments is unknown. In order to elucidate the intercompartmental relationship, several experiments were undertaken. Results are as follows: 2. The concentration of amniotic fluid PRL was different from that of maternal or fetal serum PRL during gestation. 2. There was no correlation between amniotic fluid and maternal or cord serum PRL at delivery. 3. Although bromocriptine suppressed the secretion of maternal serum PRL abruptly, the concentration of amniotic fluid PRL remained unchanged after the administration of bromocriptine at mid-gestation. 4. Analysis of molecular size of PRL by Sephadex G-100 column gel filtration revealed that the elution profiles of maternal serum PRL, fetal serum PRL, and amniotic fluid PRL differed from one another and furthermore, they were similar to those of adult pituitary PRL, fetal pituitary PRL, and decidual PRL, respectively. 5. PRL which was secreted from decidua could transfer to amniotic cavity across the fetal membrane. 6. Decidual PRL and amniotic fluid PRL have a biological activity. These results suggest that three compartments of PRL secretion during human pregnancy are independent each other and, furthermore, possible origin of amniotic fluid PRL is decidua.
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We randomly assigned 46 patients with hyperprolactinemia-induced ED to receive bromocriptine (trial group, n = 23) and bromocriptine plus CXC (control group, n = 23), respectively, both for 12 weeks. Then we compared the two groups of patients in erectile function and the levels of serum prolactin and testosterone.
Among 537 cases, 56 were included (48 men, mean age 46 years). Misuse was observed in ten cases (18%). In 25 cases (44.6%), a previous psychiatric history was documented. Main drugs involved were nervous system (63.6%) followed by respiratory (7.8%), alimentary tract and metabolism (7.8%), dermatological (5.2%) and anti-infective (5.2%) agents. Case/noncase analysis found an association with dopaminergic agonists (pergolide, pramipexole, bromocriptine, piribedil), benzodiazepines (alprazolam, bromazepam) and serotoninergic antidepressants (taken as a whole), but not antipsychotics or antiepileptics. Association was also found with varenicline, isotretinoin, interferon alpha-2b, rimonabant, benfluorex, topiramate and antiviral drugs (ribavirin, efavirenz).
Immature female rats were bilaterally lesioned in the medial preoptic area (MPOA) or hypothalamic ventromedial-arcuate region (VMAR) at 21 days of age and daily injected with the dopamine (DA) agonist bromocriptine (CB-154) through day 26. Estimation of the serum LH and FSH concentrations following ovariectomy and two injections of 0.05 micrograms oestradiol benzoate (OB)/100 g b.w. revealed that the desensitization to the negative feedback effect of OB induced by lesioning of the MPOA was almost completely prevented by CB-154. A similar effect of the drug was not found in rats lesioned in the VMAR. The DA antagonist alpha-methyldopa (alpha-MD) was then bilaterally implanted in the MPOA or VMAR of 28-day-old females. Evaluation of the gonadotrophin-inhibiting effect of OB on days 30-31 showed that medial preoptic, but not hypothalamic implants of alpha-MD reduced the sensitivity to the inhibitory action of OB. It is proposed that diminution of the dopaminergic activity in the MPOA may play a role in the prepubertal desensitization to the negative oestrogen feedback in female rats.
The effect of chronic bromocriptine administration (7.5-20 mg/day for 1-32 months) on the size of "nonsecreting" pituitary adenomas (NPA) was studied in 20 patients. Brain computed tomography showed a marked reduction of the adenoma in one patient after 1 month of treatment (7.5 mg/day); further scans taken 2 and 15 months later, under the same bromocriptine dose, did not show any other variations in the tumoral mass. In the remaining 19 patients, no changes in tumor size were documented by CT during the treatment. Four patients had a worsening of visual fields during bromocriptine administration and they were referred for neurosurgery. In conclusion, bromocriptine was ineffective in reducing tumor size in all but one patient with NPA and, in some cases, it did not prevent tumor growth as is suggested by the worsening of visual fields. Thus, bromocriptine treatment, at least at the doses capable of shrinking macroprolactinomas, seems to be of limited value in patients with NPA.
Human GH-secreting pituitary adenoma cells were cultured for periods from 4 days up to 3 weeks without or with octreotide (10 nM) and/or bromocriptine (10 nM). The effects of these drugs were measured on GH release, intracellular GH concentrations and intracellular GH mRNA levels.
No treatment is required for the postpill amenorrheic patients with normal estradiol and prolactin levels. If hyperprolactinemia is detected, bromocriptine may be used as a treatment to promote normal menstrual bleeding and ovulation.
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We have studied the effect of various agents on the decreases in striatal levels of dopamine (DA) and its metabolites which were observed 14 days after an intracerebroventricular (i.c.v.) administration of 50 micrograms 6-hydroxydopamine (6-OHDA) to mice. A pretreatment of mice with either a tyrosine hydroxylase inhibitor (alpha-methyl-p-tyrosine), a D2 receptor agonist (bromocriptine) or antagonist (haloperidol), or a vesicular uptake inhibitor (tetrabenazine) did not modify the 6-OHDA-induced decreases in DA and metabolites, indicating that DA synthesis, vesicular storage and neuronal firing rates are not mainly involved in the 6-OHDA-induced toxicity on the DA neurons. Conversely, a pretreatment with L-DOPA + benserazide potentiated the 6-OHDA-induced decreases in striatal levels of DA, homovanillic acid and 3-methoxy-tyramine. This effect was not due to an increased 6-OHDA uptake via the neuronal carrier since a pretreatment with L-DOPA + benserazide, performed 1-1.5 h before sacrifice, decreased the apparent affinity of the uptake, an effect which disappeared when considering the total DA concentration present in incubation medium ([3H]DA and cold released DA). In conclusion, potentiation of the 6-OHDA neurotoxicity by L-DOPA rises again the important problem of the safety of the latter drug in therapeutics.
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In order to investigate the role of central dopaminergic receptors in the control of vasopressin release and in cardiovascular regulation, the effects of intracerebroventricular administration of dopamine (DA) and bromocriptine (BC), a specific DA agonist, were compared in the anesthetized dog. The drugs were infused over a 20-min period into a lateral ventricle. DA brought about a transient decrease in mean arterial blood pressure, a slight increase in heart rate toward the end of the experiment, and a suppression of vasopressin release. BC increased heart rate and decreased blood pressure to a greater extent than did DA, and doubled the plasma vasopressin concentration. The increase in vasopressin secretion preceded the fall in blood pressure, ans was, therefore, due to a direct central action of BC. Although in these circumstances it is difficult to determine the role of dopaminergic neurons in the control of vasopressin release, there is some reason to believe that this role may be expressed by the actions of BC under the present experimental conditions.
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Two types of rat pituitary tumour cells secreting both prolactin (Prl) and growth hormone (GH) were cultured in vitro either on plastic dishes or on surfaces coated with an extracellular matrix (ECM) derived from bovine corneal endothelium. The presence of ECM caused an increase in Prl but a decrease in GH. On one cell line the Prl response to thyrotrophin releasing hormone (TRH) was increased by ECM. There was an increase in the rate of spread of the cultures, an increase in cell protein, and DNA synthesis and a change in cell morphology when ECM was used. It is suggested that these observations can be explained by a sensitizing action of ECM to growth factors present in serum.
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In order to study the function of the hypothalamic-pituitary-testicular axis in men referring for severe oligospermia, the hormonal pattern of 57 oligospermic men was compared to those of 19 healthy volunteers. Fourteen patients had plasma gonadotrophin levels in the normal range contrasting with low plasma testosterone (T) levels. An hyperprolactinemia was found in 2 of these men who were treated with bromocriptine. A dramatic increase in sperm count was obtained on month 9 to 12 of the therapy and 5 pregnancies were obtained. Two men with hypogonadotrophic hypogonadism and azoospermia were treated with gonadotrophins. Such a treatment induced a desquamation of immature germinal cells in the sperm on month 6 and the maturation et spermatozoa on month 18. By contrast to the latter patients, 8 men had a decrease in plasma T levels without clinical signs of hypoandrogenism. The spermocytogram showed numerous immature germinal cells. On month 7 of a treatment using gonadotrophins, the sperm count rose and 4 pregnancies were obtained after 3 to 12 months of therapy. In 2 patients an isolated FSH deficiency was suspected on the basis of undetectable FSH levels unresponsive to the infusion of GnRH. These patients were treated with hMG. This treatment induced a sharp increase in sperm count on month 6. Forty-three patients had an increase in either LH and/or FSH: 24 men had plasma testosterone and LH levels in the normal ranges, contrasting with an increase in plasma FSH level. In such men, the mean of testosterone level was significantly (p less than 0.001) lower than in controls.(ABSTRACT TRUNCATED AT 250 WORDS)
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The ascending dopamine system of the mammalian brain has been associated with motor, mnemonic and goal-directed or reward-related behaviour. The most progress in understanding the cortical mechanisms of dopaminergic modulation of function has been made with regards to short-term mnemonic (or working memory) function. Research in experimental animals strongly suggests that stimulation of dopamine D1 receptors in the prefrontal cortex can ameliorate spatial working memory related cognitive deficits, and may even enhance cognitive function in healthy animals. Research in humans has not been able to clearly replicate these findings, partly due to the lack of available agents that can safely be used. Low doses of dopamine D2 receptor agonists such as bromocriptine and pergolide may be able to enhance working memory and executive functions, but these effects may be dependent on the nature of the tasks used and the baseline performance levels of the subjects. Thus, the effects of dopaminergic cognitive enhancers may not be simple, or uniform across subjects. Systematic studies in humans carefully controlling task parameters are needed in order to specify the potential cognitive processes open to enhancement with dopaminergics. However, since the DA receptor subtypes in different brain regions appear to differentially influence similar functions, carefully defining the cognitive processes to be tested against potential therapeutics is an equally important goal. Studies in patients groups using selective dopaminergics are rather restricted, but show promise for designing large-scale clinical trials into the cognitive enhancing properties of potential therapeutic agents that act through the dopamine system.
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After treatment with CB 154 of a prolactin-secreting pituitary adenoma a morphological study reveales that many cells present a positive immunofluorescent reaction with anti-ovine prolactine antibody. At the ultra structural level, many granulations and vacuolated dense bodies can be observed.
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During and following hypoxic exposure young male hypothyroid hamsters treated with the dopamine D(2) receptor agonist bromocriptine increased breathing, while ventilation was depressed in bromocriptine-treated euthyroid hamsters. Moreover, D(2) receptor expression was increased in carotid bodies and striatum, but not in the nucleus tractus solitaries (NTS) of hypothyroid relative to euthyroid hamsters. Here ventilation was determined in older male hypothyroid and euthyroid hamsters given vehicle or bromocriptine, and exposed to baseline air, hypoxia, and then air. Bromocriptine without hypoxia served as a time control. Relative to vehicle, bromocriptine depressed ventilation in both groups exposed to air or to hypoxia, but hypothyroid bromocriptine-treated hamsters increased ventilatory responsiveness to hypoxia, while euthyroid hamsters decreased ventilatory responsiveness to hypoxia and exhibited post-hypoxic depression. Hypothyroidism had no effect on D(2) receptor expression in carotid bodies or striatum, but increased it in the NTS. Thus, in hamsters bromocriptine modulates breathing and expression of D(2) receptor depending on the length of hypothyroidism.
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Growth hormone was measured by radioimmunoassay in blood samples collected from ewes during the hormonal induction of lactation and during hand-milking post partum. Ovariectomized ewes were induced to lactate with injections of progesterone + oestradiol benzoate every 3 days for 30 days (priming phase) and then daily injections of dexamethasone for 5 days (trigger phase). The ewes were then milked daily. Immunoreactive GH levels fluctuated considerably but were generally in the range 1-15 ng/ml during all phases of lactation and were unaffected by bromocriptine treatment. Milk yield was unrelated to GH levels. Growth hormone was also measured in blood plasma taken at frequent intervals around the time of milking in lactating ewes approximately 4 weeks post partum. Although a clear prolactin response to milking was observed, there was no indication of a GH response. Although there is probably a minimum requirement for GH for lactation, a relationship between immunoreactive GH levels and milk yields was not established, perhaps because of limitations of the radioimmunoassay to detect all the biologically active GH
34 crossbred and purebred bitches referred for possible pregnancy termination. Seven additional pregnant bitches were used as controls.
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Prolactin (PRL) is synthesized by lactotropic pituitary cells. The corresponding hormonal preparations is dispensed as lactin. Bromocriptine is a dopamine agonist, dopamine being a natural inhibitor of PRL-secretion. PRL receptors in the testis are located on the interstitial cells. PRL effect on the testis depends on the age and species of animals. In the immature animals as well as in the photoperiodic ones PRL stimulates the testis development and the testicular secretion; bromocriptine decreases androgen concentration. In the postpubertal animals PRL is a melatonin antagonist in the dark time but LH synergist at the exposure to light. A high PRL concentration inhibits gonadoliberin formation, LH secretion; testosterone concentration and especially dihydrotestosterone concentration decrease (or do not change) with an elevation of estradiol level that on the whole results in feminization. The cerebral transmitters promoting or inhibiting sexual behavior are involved in the interaction with PRL. Administration of PRL, experimental or pathological hyperprolactinemia are followed by the suppression of ejaculation. Bromocriptine (parlodel) appears to be a pathogenetic therapeutic agent in hyperprolactinemia.
Long term levodopa therapy in Parkinson's disease is associated with the development of motor complications including abnormal involuntary movements and a shortening response to each dose (wearing off phenomenon). It is thought that dopamine agonists can reduce the duration of immobile off periods and the need for levodopa therapy whilst maintaining or improving motor impairments and only minimally increasing dopaminergic adverse events.
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A patient with a macroprolactinoma was treated with bromocriptine 15 mg daily. Both the size of the tumour as shown by computed tomography and the serum prolactin concentration decreased over several months but then increased. The dose of bromocriptine was increased to 40 mg daily but tumour growth continued, and the tumour was resected. Production of prolactin by cultured cells was not inhibited by high concentrations of bromocriptine, suggesting that regrowth of the tumour was due to cells resistant to dopamine agonist action. This case of regrowth of a prolactinoma during bromocriptine treatment after an initial reduction in size indicates the need for close surveillance especially of patients whose serum prolactin concentration fails to fall into the normal range with bromocriptine treatment.
Seventy-eight mothers who did not want to breast-feed their newborn infants took part in a trial to assess whether metergoline could effectively suppress puerperal lactation. Metergoline 8 mg/day was given to 69 women within 24 hours after delivery and continued for five days to prevent lactation. The remaining nine women were given a course of metergoline once lactation had started. The drug was effective in both preventing and suppressing lactation. Milk secretion, engorgement, and pain were significantly reduced in women taking metergoline. Metergoline has a similar effect to bromocriptine in suppressing lactation, but its mechanism of action remains unknown.
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First report on nine patients suffering from psoriasis who were treated with somatostatin or bromocriptin or both. These are inhibitors of HGH. The therapeutical effect on skin lesions and psoriatic alterations to joints is described.
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To investigate the potential risk for developing visual loss during single or multiple pregnancies in women with pituitary adenomas.
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Effects of dopaminergic drugs on the degranulation of mast cells (RBL-2H3 cells) and the nitric oxide production from macrophage cells (RAW 264.7) were studied. Among the dopaminergic agonists and antagonists tested, bromocriptine, 7-OH-DPAT, haloperidol, and clozapine showed potent inhibitions of mast cell degranualtion (IC50 value, 5 microM). However, these dopaminergic agents did not affect the tyrosine phosphorylations of the signaling components of the high affinity IgE receptor (FcepsilonRI), such as Syk, PLCgamma1, and PLCgamma2.; This suggested that these signaling components were not involved in the inhibition of the mast cell degranulation by these compounds. On the other hand, dopamine, bromocriptine, 7-OH-DAPT, and haloperidol markedly inhibited the nitric oxide production from RAW 264.7 cells (IC50 values, 10-20 microM). Bromocriptine, a dopamine agonist that is routinely used for the treatment of Parkinsons disease, inhibited the expression of the inducible nitric oxide synthase at an early stage of the LPS-induced protein expression in a dose-dependent manner. The results suggested that these dopaminergic agents, when used for the treatment of dopamine receptors-related diseases, such as Schizophrenia or Parkinsons disease, might have additional beneficial effects.