MELATONIN REGULATES DIURNAL CHANGES IN LOCOMOTOR ACTIVITY BY REGULATING 7alpha-HYDROXYPREGNENOLONE SYNTHESIS IN NEWTS
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1
Waseda University, Department of Biology, Japan
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2
Tokyo Gakugei University, Department of Biology, Faculty of Education, Japan
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3
University of Rouen, European Institute for Peptide Research, France
Steroids can be synthesized de novo in the central and peripheral nervous systems and such steroids are called “neurosteroids”. Seasonally breeding wild animals, such as amphibians, have served as excellent animal models to investigate the biosynthesis and biological actions of neurosteroids. Our previous studies have demonstrated that the brain of amphibians possesses the key steroidogenic enzymes and produces pregnenolone, a precursor of steroid hormones, and other various neurosteroids. We recently found that the brain of seasonally breeding newts actively produces 7alpha-hydroxypregnenolone, a previously undescribed amphibian neurosteroid. Interestingly, this novel neurosteroid acts as a neuronal modulator to stimulate locomotor activity in male newts. Because male newts show marked diurnal changes in locomotor activity, we hypothesized that 7alpha-hydroxypregnenolone may be a key factor for the induction of diurnal changes in locomotor activity in male newts. In this study, we first found diurnal changes in 7alpha-hydroxypregnenolone synthesis in the brain of male newts. The production of 7alpha-hydroxypregnenolone in the male brain increased during the dark phase when locomotor activity of males was high. Thus, diurnal changes in 7alpha-hydroxypregnenolone synthesis in the brain paralleled with locomotor activity in male newts. We then identified melatonin as a key component of the mechanism regulating 7alpha-hydroxypregnenolone synthesis. Decreased synthesis of 7alpha-hydroxypregnenolone occurred in males in vivo after melatonin removal via pinealectomy and orbital enucleation (Px plus Ex). Conversely, increased synthesis of this neurosteroid occurred after melatonin administration to Px plus Ex males. This study demonstrates that melatonin regulates synthesis of 7alpha-hydroxypregnenolone, a key factor for induction of locomotor activity, thus inducing diurnal locomotor changes in male newts
Acknowledgements
This work was supported by Grants-in-Aid for Scientific Research from the Ministry of Education, Science and Culture, Japan to KT and a Japan Society for the Promotion of Science (JSPS) – Institut National de la Santé de la Recherche Médicale (INSERM) exchange program to KT and HV.
Keywords:
7alpha-Hydroxypregnenolone,
diurnal changes,
locomotor activity,
Melatonin,
Neurosteroids,
newt brain
Conference:
NASCE 2011: The inaugural meeting of the North American Society for Comparative Endocrinology, Ann Arbor, United States, 13 Jul - 16 Jul, 2011.
Presentation Type:
Poster
Topic:
Brain and behavior
Citation:
Haraguchi
S,
Koyama
T,
Tsutsui
K and
Vaudry
H
(2011). MELATONIN REGULATES DIURNAL CHANGES IN LOCOMOTOR ACTIVITY BY REGULATING 7alpha-HYDROXYPREGNENOLONE SYNTHESIS IN NEWTS.
Front. Endocrinol.
Conference Abstract:
NASCE 2011: The inaugural meeting of the North American Society for Comparative Endocrinology.
doi: 10.3389/conf.fendo.2011.04.00021
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Received:
06 Jul 2011;
Published Online:
09 Aug 2011.
*
Correspondence:
Prof. Kazuyoshi Tsutsui, Waseda University, Department of Biology, Tokyo, 162-8480, Japan, k-tsutsui@waseda.jp