AN IN-VITRO STUDY OF THE INHIBITORY-ACTION OF METHIONINE-ENKEPHALIN ON OVARIAN MATURATION IN THE RED SWAMP CRAYFISH, PROCAMBARUS-CLARKII

The possible involvement of an endogenous opioid system in the regulat ion of ovarian development in the red swamp crayfish, Procambarus clar kii, was investigated in vitro. Ovarian explants exposed to the opioid methionine (Met) enkephalin and thoracic ganglia showed reduced devel opment in a dose-dependent manner as compared with explants incubated with thoracic ganglia alone. These thoracic ganglia secrete a gonad-st imulating hormone (GSH) as shown by the fact that explants incubated w ith thoracic ganglia alone showed more development than did explants i ncubated with muscle alone. On the other hand, the opioid antagonist n aloxone produced dose-dependent enhanced development of explants incub ated with thoracic ganglia. The fact that Met-enkephalin and naloxone are effective with thoracic ganglia in vitro strongly suggests that a functional endogenous opioid system is present in these ganglia and mo dulates release of GSH. (C) 1997 Elsevier Science Inc.