MULTIPLE FORMS OF GNRH ARE RELEASED FROM PERIFUSED MEDIAL BASAL HYPOTHALAMIC PREOPTIC AREA (MBH/POA) EXPLANTS IN BIRDS/

Both chicken gonadotropin-releasing hormones I and II (cGnRH I and II) were detected in abundant quantity by radioimmunoassay of extracts of Japanese quail medial basal hypothalamic/preoptic area (MBH/POA) frag ments that included the median eminence (ME) region. However, in radio immunoassayed extracts of Japanese quail ME alone, the concentration o f cGnRH I greatly exceeded that of cGnRH II (similar to 450 pg/ME vs < 10 pg/ME). Likewise, cGnRH I and II were released into perifusates fro m quail and turkey MBH/POA explants maintained in short-term perifusio n. Release of both forms occurred whether or not explants included the ME region, i.e., from quail POA explants that did not include the ME or from turkey MBH/POA explants from which the ME region had been diss ected out. This indicates that neuropeptides released from areas other than the ME can be a major source of neuropeptides detected in perifu sates. Further, release of cGnRH I was altered following the addition of norepinephrine to perfusion media, whereas cGnRH II release was una ffected, again, whether or not explants included the ME. These results demonstrate that the release of neurohemoral substances from perifuse d explants cannot be assumed to represent regulated secretion from the ME. (C) 1998 Academic Press.