Mode of Action and Functional Significance of 7α-Hydroxypregnenolone Stimulating Locomotor Activity

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Abstract

Previous studies over the past two decades have demonstrated that the brain and other nervous systems possess key steroidogenic enzymes and produces pregnenolone and other various neurosteroids in vertebrates in general. Recently, 7α-hydroxypregnenolone, a novel bioactive neurosteroid, was identified in the brain of newts and quail. Importantly, this novel neurosteroid is produced from pregnenolone through the enzymatic activity of cytochrome P450 _7α and acts on brain tissue as a neuronal modulator to stimulate locomotor activity in these vertebrates. Subsequently, the mode of action of 7α-hydroxypregnenolone was demonstrated. 7α-Hydroxypregnenolone stimulates locomotor activity through activation of the dopaminergic system. To understand the functional significance of 7α-hydroxypregnenolone in the regulation of locomotor activity, diurnal, and seasonal changes in 7α-hydroxypregnenolone synthesis were further characterized. Melatonin derived from the pineal gland and eyes regulates 7α-hydroxypregnenolone synthesis in the brain, thus inducing diurnal locomotor changes. Prolactin, an adenohypophyseal hormone, regulates 7α-hydroxypregnenolone synthesis in the brain, and also induces seasonal locomotor changes. In addition, 7α-hydroxypregnenolone mediates corticosterone action to modulate locomotor activity under stress. This review summarizes the current knowledge regarding the mode of action and functional significance of 7α-hydroxypregnenolone, a newly identified bioactive neurosteroid stimulating locomotor activity.

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Neuroactive steroids.

S Paul, R Purdy (1992)

Neuroactive steroids are natural or synthetic steroids that rapidly alter the excitability of neurons by binding to membrane-bound receptors such as those for inhibitory and (or) excitatory neurotransmitters. The best-studied neuroactive steroids are a series of sedative-hypnotic 3 alpha-hydroxy ring A-reduced pregnane steroids that include the major metabolites of progesterone and deoxycorticosterone, 3 alpha-hydroxy-5 alpha-pregnan-20-one (allopregnanolone) and 3 alpha,21-dihydroxy-5 alpha-pregnan-20-one (allotetrahydroDOC), respectively. These 3 alpha-hydroxysteroids do not interact with classical intracellular steroid receptors but bind stereoselectively and with high affinity to receptors for the major inhibitory neurotransmitter in brain, gamma-amino-butyric acid (GABA). Biochemical and electrophysiological studies have shown that these steroids markedly augment GABA-activated chloride ion currents in a manner similar (but not identical) to that of anesthetic barbiturates. Several steroids have also been observed to have convulsant or proconvulsant properties, including the synthetic amidine 3 alpha-hydroxy-16-imino-5 beta-17-azaandrostan-11-one (RU5135) and the natural sulfate esters of pregnenolone and dehydroepiandrosterone. Several of these have been shown to be bicuculline or picrotoxin-like GABAA receptor antagonists. Examples of steroids that alter neuronal excitability rapidly by augmenting or inhibiting excitatory amino acid receptor-mediated responses have also been reported. Recently, allopregnanolone and allotetrahydroDOC have also been measured in brain and plasma where their levels have been shown to fluctuate in response to stress and during the estrous and menstrual cycles of rats and humans, respectively. Although the major fraction of allopregnanolone in tissue, including brain, is of adrenal and/or ovarian origin, appreciable levels of allopregnanolone can still be measured in the brains of adrenalectomized and/or oophorectomized animals. Receptor-active neurosteroids may represent an important class of neuromodulators that can rapidly alter central nervous system excitability via novel nongenomic mechanisms.

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Neurosteroids: biosynthesis and function of these novel neuromodulators.

Nathalie Compagnone, V Mellon (1999)

Over the past decade, it has become clear that the brain is a steroidogenic organ. The steroids synthesized by the brain and nervous system, given the name neurosteroids, have a wide variety of diverse functions. In general, they mediate their actions, not through classic steroid hormone nuclear receptors, but through ion-gated neurotransmitter receptors. This paper summarizes what is known about the biosynthesis of neurosteroids, the enzymes mediating these reactions, their localization during development and in the adult, and their function and mechanisms of action in the developing and adult central and peripheral nervous systems. The expression of the steroidogenic enzymes is developmentally regulated, with some enzymes being expressed only during development, while others are expressed during development and in the adult. These enzymes are expressed in both neurons and glia, suggesting that these two cell types must work in concert to produce the appropriate active neurosteroid. The functions attributed to specific neurosteroids include modulation of GABA(A) and NMDA function, modulation of sigma receptor function, regulation of myelinization, neuroprotection, and growth of axons and dendrites. Neurosteroids have also been shown to modulate expression of particular subunits of GABA(A) and NMDA receptors, providing additional sites at which these compounds can regulate neural function. The pharmacological properties of specific neurosteroids are described, and potential uses of neurosteroids in specific neuropathologies and during normal aging in humans are also discussed. Copyright 2000 Academic Press.

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Acute corticosterone treatment is sufficient to induce anxiety and amygdaloid dendritic hypertrophy.

R Sapolsky, Soma R. Mitra (2008)

Stress is known to induce dendritic hypertrophy in the basolateral amygdala (BLA) and to enhance anxiety. Stress also leads to secretion of glucocorticoids (GC), and the BLA has a high concentration of glucocorticoid receptors. This raises the possibility that stress-induced elevation in GC secretion might directly affect amygdaloid neurons. To address the possible effects of GC on neurons of amygdala and on anxiety, we used rats treated either acutely with a single dose or chronically with 10 daily doses of high physiological levels of corticosterone (the rat-specific glucocorticoid). Behavior and morphological changes in neurons of BLA were measured 12 days after the initiation of treatment in both groups. A single acute dose of corticosterone was sufficient to induce dendritic hypertrophy in the BLA and heightened anxiety, as measured on an elevated plus maze. Moreover, this form of dendritic hypertrophy after acute treatment was of a magnitude similar to that caused by chronic treatment. Thus, plasticity of BLA neurons is sufficiently sensitive so as to be saturated by a single day of stress. The effects of corticosterone were specific to anxiety, as neither acute nor chronic treatment caused any change in conditioned fear or in general locomotor activity in these animals.

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Author and article information

Journal

Journal ID (nlm-ta): Front Endocrinol (Lausanne)

Journal ID (iso-abbrev): Front Endocrinol (Lausanne)

Journal ID (publisher-id): Front. Endocrin.

Title: Frontiers in Endocrinology

Publisher: Frontiers Research Foundation

ISSN (Electronic): 1664-2392

Publication date (Electronic preprint): 29 June 2011

Publication date (Electronic): 22 August 2011

Publication date Collection: 2011

Volume: 2

Electronic Location Identifier: 23

Affiliations

[1] ¹simpleLaboratory of Integrative Brain Sciences, Department of Biology, Waseda University, and Center for Medical Life Science of Waseda University Tokyo, Japan

[2] ²simpleLaboratory of Neuronal and Neuroendocrine Differentiation and Communication (INSERM U982), European Institute for Peptide Research, University of Rouen Mont-Saint-Aignan, France

Author notes

Edited by: Eric W. Roubos, Radboud University Nijmegen, Netherlands

Reviewed by: Gilberto Mosconi, University of Camerino, Italy; H. Bobby Fokidis, University of British Columbia, Canada

*Correspondence: Kazuyoshi Tsutsui, Laboratory of Integrative Brain Sciences, Department of Biology, Waseda University, and Center for Medical Life Science of Waseda University, 2-2 Wakamatsu-cho, Shinjuku-ku, Tokyo 162-8480, Japan. e-mail: k-tsutsui@ 123456waseda.jp

This article was submitted to Frontiers in Neuroendocrine Science, a specialty of Frontiers in Endocrinology.

Article

DOI: 10.3389/fendo.2011.00023

PMC ID: 3355833

PubMed ID: 22645507

SO-VID: 795a17a2-36e2-4bc7-8b90-8181780cc619

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This is an open-access article subject to a non-exclusive license between the authors and Frontiers Media SA, which permits use, distribution and reproduction in other forums, provided the original authors and source are credited and other Frontiers conditions are complied with.

History

Date received : 14 May 2011

Date accepted : 04 August 2011

Page count

Figures: 4, Tables: 0, Equations: 0, References: 84, Pages: 8, Words: 7283

Mode of Action and Functional Significance of 7α-Hydroxypregnenolone Stimulating Locomotor Activity

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Karger: Endocrinology

Most cited references 78

Neuroactive steroids.

Neurosteroids: biosynthesis and function of these novel neuromodulators.

Acute corticosterone treatment is sufficient to induce anxiety and amygdaloid dendritic hypertrophy.

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