@article {8430, title = {Pituitary Hormones mRNA Abundance in the Mediterranean Sea Bass Dicentrarchus labrax: Seasonal Rhythms, Effects of Melatonin and Water Salinity}, journal = {Frontiers in Physiology}, volume = {12}, year = {2021}, month = {12/15/2021}, pages = {774975}, type = {Research article}, abstract = {In fish, most hormonal productions of the pituitary gland display daily and/or seasonal
rhythmic patterns under control by upstream regulators, including internal biological
clocks. The pineal hormone melatonin, one main output of the clocks, acts at different
levels of the neuroendocrine axis. Melatonin rhythmic production is synchronized mainly
by photoperiod and temperature. Here we aimed at better understanding the role
melatonin plays in regulating the pituitary hormonal productions in a species of scientific
and economical interest, the euryhaline European sea bass Dicentrarchus labrax. We
investigated the seasonal variations in mRNA abundance of pituitary hormones in two
groups of fish raised one in sea water (SW fish), and one in brackish water (BW fish). The
mRNA abundance of three melatonin receptors was also studied in the SW fish. Finally,
we investigated the in vitro effects of melatonin or analogs on the mRNA abundance of
pituitary hormones at two times of the year and after adaptation to different salinities.
We found that (1) the reproductive hormones displayed similar mRNA seasonal profiles
regardless of the fish origin, while (2) the other hormones exhibited different patterns
in the SW vs. the BW fish. (3) The melatonin receptors mRNA abundance displayed
seasonal variations in the SW fish. (4) Melatonin affected mRNA abundance of most
of the pituitary hormones in vitro; (5) the responses to melatonin depended on its
concentration, the month investigated and the salinity at which the fish were previously
adapted. Our results suggest that the productions of the pituitary are a response to
multiple factors from internal and external origin including melatonin. The variety of the
responses described might reflect a high plasticity of the pituitary in a fish that faces
multiple external conditions along its life characterized by marked daily and seasonal
changes in photoperiod, temperature and salinity.}, keywords = {annual variations, hormones, melatonin, photoperiod, pituitary, salinity, sea bass}, doi = {10.3389/fphys.2021.774975}, url = {https://www.frontiersin.org/articles/10.3389/fphys.2021.774975/full?\&utm_source=Email_to_authors_\&utm_medium=Email\&utm_content=T1_11.5e1_author\&utm_campaign=Email_publication\&field=\&journalName=Frontiers_in_Physiology\&id=774975}, author = {Jack Falcon}, editor = {Maria-Jesus Herrero and Laura-Gabriela Nisembaum} }