Diel variations in arginine vasotocin content of goldfish brain and pituitary: effects of photoperiod and pinealectomy.
Arginine vasotocin (AVT) content was determined in the telencephalon, the hypothalamus, and the pituitary gland of sham-operated and pinealectomized goldfish subjected to 20 degrees and 12/12LD or 24DD photoperiods in winter or spring. The tissues collected at 1000 or 2200 hr were homogenized and extracted in acetic acid. Hypothalamic and telencephalic AVT content, determined by radioimmunoassay, fluctuated throughout the light-dark cycle; AVT content was higher at 2200 than at 1000 hr under the 12/12LD photoperiod. No fluctuations were detected in pituitary AVT content. Telencephalic AVT did not fluctuate under constant darkness, and hypothalamic AVT increased and pituitary AVT decreased compared to the AVT content detected in the 12/12LD groups. No significant effects of pinealectomy or season on AVT levels in the telencephalon, hypothalamus, and the pituitary were evident. The results indicate that AVT content within the preoptico-neurohypophyseal system of the goldfish fluctuate within 24-hr periods and that photoperiod has an effect on the pattern of these fluctuations. The photoperiodic influences do not seem to be mediated by the pineal organ.
D000818:Animals; D001923:Brain Chemistry; D002940:Circadian Rhythm; D003530:Cyprinidae / Q000502:physiology*; D006054:Goldfish / Q000502:physiology*; D008027:Light; D010870:Pineal Gland / Q000502:physiology*; D010902:Pituitary Gland / Q000032:analysis*; D014018:Tissue Distribution; D014668:Vasotocin / Q000032:analysis*
D014668:Vasotocin