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Neonatal Hormone Treatment and Maturation of the Pineal Noradrenergic System: Hydrocortisone and Thyroxine
Author(s) -
Yuwiler A.,
Brammer Gary L.
Publication year - 1981
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1981.tb04485.x
Subject(s) - medicine , endocrinology , norepinephrine , circadian rhythm , serotonin , desipramine , hormone , hydrocortisone , melatonin , biology , epinephrine , chemistry , dopamine , receptor , antidepressant , hippocampus
The circadian release of norepinephrine from nerve terminals in the pineal gland drives acetyl‐CoA:serotonin N ‐acetyltransferase (NAT; EC 2.3.1.5) activity in the adult pineal from a daytime low to a nighttime high. In the newborn, enzyme activity is intermediate between the adult's daily extremes and has only a small circadian fluctuation. With age, these fluctuations increase in amplitude until the adult pattern is attained at about days 10–12. Treatment of neonates with thyroxine for the first 3 days of life accelerated, whereas administration of hydrocortisone acetate at birth retarded the developmental decline in daytime serotonin‐N‐acetyltransferase activity. Maximal differences in daytime enzyme activity of controls and thyroxine‐treated animals were seen at day 4 and between controls and steroid‐treated pups at day 8. Desipramine treatment increased NAT activity in 8‐day‐old animals; hydrocortisone‐treated animals were least affected. Freshly cultured pineals from steroid‐treated animals were more responsive to low, and less responsive to high, concentrations of norepinephrine than glands from thyroxine‐treated or control animals. They were also less responsive to isoproterenol both in acute and 48‐h organ culture. Pineals from hydrocortisone‐treated animals in culture accumulated less exogeneous norepinephrine than glands from controls but released a greater fraction of their content on transfer to fresh medium. Normal and steroid‐treated animals released the same fraction of their norepinephrine contents into the medium when reuptake was blocked by desipramine (DMI).