Persistence of the nychthemeral rhythm of melatonin secretion in pinealectomized or optic tract-sectioned trout (Salmo gairdneri)
✍ Scribed by Gern, William A. ;Owens, David W. ;Ralph, Charles L.
- Publisher
- John Wiley and Sons
- Year
- 1978
- Tongue
- English
- Weight
- 484 KB
- Volume
- 205
- Category
- Article
- ISSN
- 0022-104X
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✦ Synopsis
Abstract
In a preliminary investigation, what appeared to be melatonin was measured in the plasma of pinealectomized trout using a specific and sensitive radioimmunoassay. Later, following the combined procedures of thin‐layer chromatography and radioimmunoassay, the immunogenic molecule measured in pinealectomized trout plasma was verified as melatonin. After this validation procedure, plasma melatonin titers were assessed using RIA in pinealectomized, sham pinealectomized or intact rainbow trout either at mid‐photophase or mid‐scotophase. Results demonstrated that pinealectomy significantly reduced plasma melatonin measured at mid‐scotophase, compared to the midscotophase values for either the sham‐operated or intact animals. Interestingly, pinealectomized animals continued to show significantly elevated, mid‐scotophase plasma melatonin titers when compared to the mid‐photophase values. The same was true for the sham‐operated and intact groups.
In a second experiment, it was found that severing the optic tract (optictract‐section) did not alter the rhythm of melatonin measured in the plasma. This indicates that the trout pineal may monitor the environmental photoperiod directly, thereby controlling the rhythmic fluctuations in plasma melatonin. Optic tract‐section did cause a significant increase in the mid‐scotophase melatonin titer. This increase may be due to stress caused by sensory deprivation.