“…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).…”