title: Pineal-gonadal relationship in the teleost Channa punctatus (Bloch): evidence for possible involvement of hypothalamic serotonergic system.
abstract: In Channa punctatus, pinealectomy results in an accelerated growth (stimulatory effect) of the ovary in preparatory phase (March), but had no significant effect in prespawning (May-June) or postspawning (September) phases. Administration of melatonin (25 micrograms/fish or 0.4 mg/kg BW at 2-day intervals for 30 days) inhibits the stimulatory effect of a long photoperiod and high temperature (16L:8D; 22 +/- 1 degree C) on the ovary in the early preparatory phase (February). In the late preparatory phase (April), the administration of both melatonin (0.5 mg/kg BW at 2-day intervals) and parachlorophenylalanine (pCPA, a serotonin synthesis blocker; 100 mg/kg BW at 3-day intervals) for 30 days inhibits ovarian activity in comparison to that of the saline-treated control group. In the dose-response study, greater than or equal to 0.5 mg/kg BW of melatonin induced a significant increase in hypothalamic 5-HT content and greater than or equal to 10 mg/kg BW of pCPA decreased it significantly. In the time-course study, melatonin (2.0 mg/kg BW) elevates the 5-HT content significantly after an hr of the injection and maintained it up to 48 hrs. The administration of pCPA (200 mg/kg BW) had significantly inhibited the 5-HT content which was sustained for 72 hr. In another study, a single injection of melatonin (0.5 mg/kg BW) increased the 5-HT content significantly. A single injection of pCPA (100 mg/kg BW) decreased significantly both the content and activity of 5-HT. It is inferred that hypothalamic 5-HT may play a central role in photosexual mechanisms and mediate long photoperiodic effects on neuroendocrine-reproductive axis.
authors.affiliation: Department of Zoology, Banaras Hindu University, Varanasi, India.
authors.forename: K P
authors.initials: KP
authors.lastname: Joy
authors.forename: I A
authors.initials: IA
authors.lastname: Khan
mesh_terms: D000818:Animals; D002940:Circadian Rhythm; D004305:Dose-Response Relationship, Drug; D005260:Female; D010134:Fenclonine / Q000494:pharmacology; D005399:Fishes / Q000502:physiology*; D006358:Hot Temperature; D007031:Hypothalamus / Q000378:metabolism*; D008550:Melatonin / Q000494:pharmacology; D009865:Oocytes / Q000187:drug effects; D010053:Ovary / Q000502:physiology*; D010870:Pineal Gland / Q000502:physiology* / Q000601:surgery; D012621:Seasons; D012701:Serotonin / Q000378:metabolism*
chemical_list: D012701:Serotonin; D008550:Melatonin; D010134:Fenclonine