Effects of Endorphins on Prolactin and Growth Hormone Secretion in Rats

Immunoreactive β-Endorphin and Adrenocorticotropin in Human Cerebrospinal Fluid

“…CSF /3-EP-LI and ACTH-LI levels in acromegaly are of interest, because intraventricular administration of,endorphin stimulates growth hormone secretion in animals (42). In this study, however, CSF ,3-EP-LI and ACTH-LI levels in acromegaly did not differ from those in the control group and the gel chromatographic pattern of CSF ,3-EP-LI from a patient with acromegaly was similar to those of other subjects.…”

Morphine stimulates prolactin release in normal but not in castrated male rats

“…administration of 500 µg metenkephalin to normal adult male rats causes a significant rise in serum prolactin concentrations and that the same treatment results in a much lower release of prolactin in orchidectomized rats. Kato et al (1982) have found that beta-endorphin induces an increase of plasma prolactin in castrated male rats, which is almost 10 times lower than that observed in normal animals (Kato et al, 1978). Moreover, Forman, Sonntag, Miki, Ramos & Meites (1981) have reported that the stimulatory effect of morphine on prolactin release is decreased in aged male rats, which are known to have serum testosterone levels lower than those of younger animals.…”

“…It has also been demonstrated that specific opioid antagonists (e.g. naloxone and naltrexone) may prevent the rise of prolactin secretion induced by the opioids (Rivier, Vale, Ling, Brown & Guillemin, 1977;Chihara, Arimura, Coy & Schally, 1978;Kato, Iwasaki, Abe, Ohgo & Imura, 1978;Meites et al, 1979; Koenig, Mayfield, Coppings, McCann & Krulich, 1980;Panerai, Casanueva, Martini, Mantegazza & Di Giulio, 1981;Van Vugt, Sylvester, Aylsworth & Meites, 1981;Kato et al, 1982). Some authors have also found that opioid antagonists may reduce basal serum concentrations of prolactin (Meites et al, 1979), but this finding has not been confirmed by others (Martin, Tolis, Woods & Guyda, 1979;Mioduszewski, Zimmerman & Critchlow, 1982;Giudici et al, 1984).…”

“…(Rivier et al, 1977;Chihara et al, 1978;Kato et al, 1978Kato et al, ,1982Panerai et al, 1981;Van Vugt et al, 1981;Matsushita et al, 1982;Giudici etal, 1984). The experiments performed in long-term castrated rats clearly show that even the i.v.t.…”

Involvement of brain dopamine in prolactin secretion induced by a synthetic Met5-enkephalin analogue in rats.

“…On the other hand, there are such substances in the brain as serotonin (Iwasaki et al, 1978;Kamberi et al, 1971), histamine (Donoso et al, 1976;Libertun et al, 1976), TRH (Bower et al, 1971;Tashijian et al, 1971) and VIP (Kato et al, 1978b;Ruberg et al, 1978) that seems to play a stimulatory role in PRL release. Recently, morphinomimetic peptides have been isolated from the mammalian central nervous system (Cox et al, 1976;Hughes et al, 1975) and subsequently they have been proved to stimulate PRL secretion (Bruni et al, 1977;Dupont et al, 1977;Ferland et al, 1977;Kato et al, 1978a;Rivier et al, 1977a). However, the interaction of these opioid peptides with brain amines and other neuropeptides has not been fully elucidated.…”