Regulation of the stress-responsive X-organ--Y-organ axis by 5-hydroxytryptamine in the crab, Cancer antennarius.
Eyestalk-intact, but not de-eyestalked, crabs (Cancer antennarius) given five injections of 5-hydroxytryptamine (5HT, 750 micrograms per injection) in 48 hr showed significant reductions in hemolymph ecdysteroid titers within the first 12 hr which continued through Hour 72; the effect was reversible (Hours 72-144). The 5HT synthesis inhibitor p-chlorophenylalanine (PCPA; 60 micrograms) or the 5HT receptor antagonist cyproheptadine (CPH; 100 micrograms) caused significant rises in serum ecdysteroids in intact, but not in de-eyestalked, crabs; with four injections over 48 hr, a rise was evident at 12 hr, continued through 72 hr, and returned to control levels within 4 days post-treatment. Stress due to handling depressed ecdysteroid levels, an effect that was reversed by PCPA and CPH; values in the treated groups returned to prestress levels within 24 hr and were significantly greater than prestress levels within 48 hr. 5HT treatment did not further decrease stress-reduced ecdysteroid titers. Normal behaviors are described in posturing and in defensive responses to stress; these were changed in both intact and de-eyestalked crabs by 5HT treatment (but not by PCPA or CPH). These findings support the hypothesis that release of molt-inhibiting hormone (MIH) from crab eyestalks is mediated by 5HT and suggest that stress induces 5HT-mediated MIH release.
D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects; D003386:Brachyura / Q000502:physiology*; D003533:Cyproheptadine / Q000494:pharmacology; D026461:Ecdysteroids; D005123:Eye / Q000187:drug effects / Q000503:physiopathology*; D005260:Female; D010134:Fenclonine / Q000494:pharmacology; D006458:Hemolymph / Q000378:metabolism; D007447:Invertebrate Hormones / Q000097:blood; D012701:Serotonin / Q000494:pharmacology*; D013312:Stress, Physiological / Q000503:physiopathology*
D026461:Ecdysteroids; D007447:Invertebrate Hormones; D003533:Cyproheptadine; D012701:Serotonin; D010134:Fenclonine