MODE OF ACTION OF THE NEUROTRANSMITTER 5-HYDROXYTRYPTAMINE IN STIMULATING OVARIAN MATURATION IN THE RED SWAMP CRAYFISH, PROCAMBARUS-CLARKII- AN IN-VIVO AND IN-VITRO STUDY

Ovarian explants from the red swamp crayfish, Procambarus clarkii, wer e incubated with 5-hydroxytryptamine (5-HT) and muscle, and with 5-HT in combination with eyestalk tissue, brains, or thoracic ganglia. In v itro, 5-HT without brain or thoracic ganglia in the incubation medium had no significant effect on the ovarian explants. In contrast, in vit ro brains and thoracic ganglia induced ovarian maturation, indicating the presence of a gonad-stimulating hormone (GSH) in these tissues. Ho wever, this in vitro stimulatory effect was significantly greater when 5-HT was present in the incubation medium with the brains and thoraci c ganglia. These results provide in vitro evidence in support of the h ypothesis that the previously observed in vivo stimulatory action of 5 -HT on the ovaries is an indirect one, 5-HT acting to stimulate releas e of a GSH. (C) 1995 Wiley-Liss, Inc.