Topic
Prolactin
About: Prolactin is a research topic. Over the lifetime, 22356 publications have been published within this topic receiving 609537 citations. The topic is also known as: lactotropin, & PRL,.
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TL;DR: Data suggest that these atypical antipsychotics raise prolactin levels, although the increases with olanzapine did not reach statistical significance.
Abstract: OBJECTIVE: Atypical antipsychotics are thought not to elevate prolactin levels. The authors examined data suggesting that atypical antipsychotics do elevate prolactin levels but more transiently than typical antipsychotics. METHOD: Prolactin levels in 18 male patients with schizophrenia who were receiving atypical antipsychotics were monitored over the 24-hour period following administration of their daily oral dose of risperidone, olanzapine, or clozapine. RESULTS: The baseline prolactin levels in patients receiving risperidone (mean=27 ng/ml, SD=14) were abnormally high, but baseline prolactin levels in patients receiving olanzapine (mean=9 ng/ml, SD=5) and clozapine (mean=9 ng/ml, SD=5) were not high. All three atypical antipsychotics caused a doubling of prolactin levels over baseline levels 6 hours after medication administration. CONCLUSIONS: These data suggest that these atypical antipsychotics raise prolactin levels, although the increases with olanzapine did not reach statistical significance. Th...
179 citations
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TL;DR: Using naltrexone as a tool to block opiate receptor function, it is explored whether endorphins are tonically involved as a putative neurotransmitter in the regulation of prolactin release and demonstrates a new instance where an opiate antagonist modifies normal function.
Abstract: ENDORPHINS, the endogenous peptides recently isolated and identified in brain have been implicated in regulation of pain1–4. But their wide distribution throughout the brain5–7 and their profound behavioural effects after central administration8 suggest an involvement in other central nervous system processes. Immunohistochemical identification of these endorphins (refs 9, 10 and F. Bloom, personal communication) in hypothalamic neurones indicated that neuroendocrine effects are probable. Morphine was previously reported to block ovulation, while more recently, morphine11 and endorphins12–14 were observed to stimulate release of prolactin and growth hormone. Yet, these observations have not established a direct, tonic participation of endorphins in hypothalamic and anterior pituitary function. The absence of any direct action of opiate antagonists has been taken as an argument against any tonic role of endorphins. Recent reports indicate, however, that opiate antagonists do modify on-going central processes. For example, naloxone and naltrexone lower pain threshold in appropriate conditions in man and experimental animals15–18. Using naltrexone as a tool to block opiate receptor function, we have explored whether endorphins are tonically involved as a putative neurotransmitter in the regulation of prolactin release. The results presented here demonstrate a new instance where an opiate antagonist modifies normal function. The data agree with a preliminary report indicating that naloxone reduced prolactin release in immature female rats19.
178 citations
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TL;DR: The circadian rhythms of plasma levels of melatonin, prolactin and LH are not modified in old age nor in dementia, and a positive correlation has been demonstrated in young men between melatonin and LH and betweenmelatonin and Prolactin, but no such correlation could be found in the elderly.
Abstract: Circadian changes in plasma levels of melatonin, prolactin, LH and FSH were studied in four groups: seven healthy young men, six elderly men, six elderly women and six elderly demented patients (two men and four women). The daily activities of the subjects were synchronous and blood samples were taken every 4 h. The 24-h mean concentrations of prolactin in plasma were the same in all groups, whereas those of LH and FSh were twice as high in the elderly as in the young men and eight and 23 times higher respectively in the elderly women. The 24-h mean plasma levels of melatonin in the elderly were half those in the young, but were not influenced by the sex or mental condition of the subjects. A statistically significant circadian rhythm for melatonin was defined in the four groups, for prolactin in all groups except the elderly men and for LH only in the demented patients and in the young men. No circadian rhythm could be detected for FSH in any of the four groups. The acrophases of melatonin and prolactin ranged between 02.30 and 04.00 h, those of LH (when a rhythm was validated) clustered around 01.00 h. The circadian rhythms of plasma levels of melatonin, prolactin and LH are not modified in old age nor in dementia. A positive correlation has been demonstrated in young men between melatonin and LH and between melatonin and prolactin, but no such correlation could be found in the elderly.
178 citations
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TL;DR: The results suggest that mammosomatotropes, cells that secrete both GH and PRL, may exist in pituitaries of normal rats.
Abstract: Sequential application of reverse hemolytic plaque assays for GH and PRL revealed the presence of individual pituitary cells that released both hormones. These dual cells accounted for approximately one third of all GH and/or PRL secretors in 24-h pituitary cultures derived from male rats. Additional studies in which a different version of the plaque assay and double-staining immunocytochemistry were applied separately to dispersed pituitary cells from males yielded results that were virtually identical. These results suggest that mammosomatotropes, cells that secrete both GH and PRL, may exist in pituitaries of normal rats. (Endocrinology 116: 734-737,1985)
178 citations
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TL;DR: The presence of Gn RH receptors in the testis indicates that these sites mediate the direct inhibitory actions of GnRH agonists upon testicular endocrine function.
Abstract: Agonist analogs of gonadotropin-releasing hormone (GnRH) have been shown to exert antigonadal effects in male and female animals. In hypophysectomized male rats treated with follicle-stimulating hormone, administration of a potent GnRH agonist caused depletion of luteinizing hormone and prolactin receptors and marked suppression of serum testosterone levels. The possibility that such direct effects of GnRH agonists on testicular function could be expressed through specific receptors located in the interstitial cells of the testis was supported by the selective concentration of a 125I-labeled GnRH agonist by the testis in vivo. Specific receptors for the releasing hormone were demonstrated in testis particles and dispersed interstitial cells by direct binding analysis with the 125I-labeled GnRH agonist. The binding affinity (Ka = G X 10(9) M-1) and peptide specificity of the testicular GnRH binding sites were similar to those of anterior pituitary and ovarian GnRH receptors. The presence of GnRH receptors in the testis indicates that these sites mediate the direct inhibitory actions of GnRH agonists upon testicular endocrine function.
178 citations