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Effects of Acute and Chronic Administration of Neurosteroid Dehydroepiandrosterone Sulfate on Neuronal Excitability in Mice

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Effects of Acute and Chronic Administration of Neurosteroid Dehydroepiandrosterone Sulfate on Neuronal Excitability in Mice Journal name: Drug Design, Development and Therapy Article Designation: Original Research Year: 2016 Volume: 10 Drug Design, Development and Therapy Dovepress Running head verso: Svob Strac et al Running head recto: Effects of DHEAS on neuronal excitability open access to scientific and medical research DOI: http://dx.doi.org/10.2147/DDDT.S102102 Open Access Full Text Article ORIGINAL RESEARCH Effects of acute and chronic administration of neurosteroid dehydroepiandrosterone sulfate on neuronal excitability in mice Dubravka Svob Strac1 Background: Neurosteroid dehydroepiandrosterone sulfate (DHEAS) has been associated Josipa Vlainic1 with important brain functions, including neuronal survival, memory, and behavior, showing Janko Samardzic2 therapeutic potential in various neuropsychiatric and cognitive disorders. However, the 3 antagonistic effects of DHEAS on -amino-butyric acid receptors and its facilitatory action Julija Erhardt γ A Zeljka Krsnik4 on glutamatergic neurotransmission might lead to enhanced brain excitability and seizures and thus limit DHEAS therapeutic applications. The aim of this study was to investigate possible 1Laboratory for Molecular age and sex differences in the neuronal excitability of the mice following acute and chronic Neuropsychiatry, Division of Molecular Medicine, Rudjer Boskovic DHEAS administration. 2 Institute, Zagreb, Croatia; Institute of Methods: DHEAS was administered intraperitoneally in male and female adult and old mice Pharmacology, Clinical Pharmacology For personal use only. and Toxicology, Medical Faculty, either acutely or repeatedly once daily for 4 weeks in a 10 mg/kg dose. To investigate the poten- University of Belgrade, Belgrade, tial proconvulsant properties of DHEAS, we studied the effects of acute and chronic DHEAS 3 Serbia; Department of Animal treatment on picrotoxin-, pentylentetrazole-, and N-methyl-D-aspartate-induced seizures in Physiology, Faculty of Science, University of Zagreb, 4Croatian mice. The effects of acute and chronic DHEAS administration on the locomotor activity, motor Institute for Brain Research, coordination, and body weight of the mice were also studied. We also investigated the effects Department of Neuroscience, School of DHEAS treatment on [3H]flunitrazepam binding to the mouse brain membranes. of Medicine, University of Zagreb, Zagreb, Croatia Results: DHEAS did not modify the locomotor activity, motor coordination, body weight, and brain [3H]flunitrazepam binding of male and female mice. The results failed to demonstrate significant effects of single- and long-term DHEAS treatment on the convulsive susceptibility in both adult and aged mice of both sexes. However, small but significant changes regarding sex differences in the susceptibility to seizures were observed following DHEAS administra- tion to mice. Conclusion: Although our findings suggest that DHEAS treatment might be safe for various Drug Design, Development and Therapy downloaded from https://www.dovepress.com/ by 54.70.40.11 on 28-Apr-2018 potential therapeutic applications in adult as well as in old age, they also support subtle inter- action of DHEAS with male and female hormonal status, which may underline observed sex differences in the relationship between DHEAS and various health outcomes. Keywords: dehydroepiandrosterone sulfate, mice, age and sex differences, seizure threshold, motor activity, [3H]flunitrazepam binding Introduction Dehydroepiandrosterone sulfate (DHEAS) is a neurosteroid associated with various important functions in the mammalian brain.1–4 Namely, DHEAS has been reported to Correspondence: Dubravka Svob Strac modulate neuronal plasticity,5–9 cognition, and emotions,10–15 thus showing therapeutic Division of Molecular Medicine, Rudjer potential in a variety of neuropsychiatric and cognitive disorders.2,16–20 It appears that Boskovic Institute, Bijenicka cesta 54, 10 000 Zagreb, Croatia the effects of DHEAS in the central nervous system are mediated through its action on Tel +385 1 457 1268 multiple signaling pathways and neurotransmitter systems, which are also involved in Fax +385 1 456 1010 Email [email protected] regulating the balance between excitation and inhibition in the brain.3,15,21–23 Perhaps, the submit your manuscript | www.dovepress.com Drug Design, Development and Therapy 2016:10 1201–1215 1201 Dovepress © 2016 Svob Strac et al. This work is published and licensed by Dove Medical Press Limited. The full terms of this license are available at https://www.dovepress.com/terms.php and incorporate the Creative Commons Attribution – Non Commercial (unported, v3.0) License (http://creativecommons.org/licenses/by-nc/3.0/). By accessing the work you http://dx.doi.org/10.2147/DDDT.S102102 hereby accept the Terms. Non-commercial uses of the work are permitted without any further permission from Dove Medical Press Limited, provided the work is properly attributed. For permission for commercial use of this work, please see paragraphs 4.2 and 5 of our Terms (https://www.dovepress.com/terms.php). Powered by TCPDF (www.tcpdf.org) 1 / 1 Svob Strac et al Dovepress most documented has been the ability of DHEAS to bind and body weight in mice following acute and chronic DHEAS allosterically modulate the γ-amino-butyric acidA (GABAA) administration. receptor complex.3,15,21,24 In addition to its antagonistic effects In addition, sex differences in the seizure sensitivity might 25–30 on GABAA receptors, DHEAS has been shown to act be due to the different modulation of the neurotransmitter as a positive modulator of N-methyl-D-aspartate (NMDA) receptor activity by DHEAS-derived sexual hormones and receptors and facilitate NMDA-mediated glutamatergic neu- their metabolites. Therefore, we also studied the potential 31,32 rotransmission through central sigma receptors. changes in the action of DHEAS at GABAA receptors using Some of these actions of DHEAS might lead to enhanced [3H]flunitrazepam binding on the brain membranes obtained brain excitability and possible seizures33 and thus limit its from male and female mice following DHEAS treatment. potential therapeutic applications. Increase in the motor activ- ity and body weight reduction may also appear consistently Materials and methods with potential proconvulsive, anxiogenic, and provoking Animals effects of DHEAS.34,35 However, it is not yet fully elucidated Adult (∼3 months old, weighing 20–25 g) and aged (∼18 months to what extent DHEAS complex pharmacological profile old, weighing 30–45 g) male and female CBA mice, bred in contributes to its central actions, so the actual in vivo effects Rudjer Boskovic Institute, Zagreb, Croatia, were used. The ani- of DHEAS remain uncertain. Namely, in contrast to the mals were housed at a constant temperature (22°C) and under reports suggesting that DHEAS can induce seizures when a light cycle of 12-hour light/12-hour darkness (lights on at 7 administered systemically or directly into the brain,35,36 other am). Food and water were freely available. Mice were caged in studies failed to confirm proconvulsant effects of DHEAS.37–41 groups of ten. As the female mice were caged next to the male Moreover, there is also a variety of data regarding the effects mice, their estrus cycle was presumably synchronized due to the of DHEAS on the motor activity and body weight of the Whitten effect.55 All animal care and experimental procedures animals.34,37,42–45 were carried out in accordance with the Directive 2010/63/EU Observed age-related decline in DHEAS levels sug- of European Parliament and Council of the European Union For personal use only. gests possible role of this neurosteroid in many disorders of on the protection of animals used for scientific purposes and aging.2,46,47 Low DHEAS levels have been associated with the Croatian law on animal welfare. The ethical approval was age-related changes and decreased lifespan in various animal obtained from Rudjer Boskovic Bioethics Committee. studies,48 while exogenous DHEAS has been suggested to effectively ameliorate aging symptoms.49 However, the find- Drugs ings of some studies are inconsistent or negative. DHEAS (Aldrich Chemical Co, St Louis, Mo, USA), penty- Although observed beneficial effects of DHEAS, such lenetetrazole (PTZ, Sigma-Aldrich Co., St Louis, MO, USA), as proimmune, antidiabetic, antiobesity, antiatherosclerosis, picrotoxin (Sigma), and NMDA (Ascent Scientific, Bristol, antiosteoporosis, anticarcinogenic, antidementia, antiaging, UK) were dissolved in saline. Following the determination and many other effects,50,51 probably require rather long-term of animal body weight, DHEAS or saline was administered therapeutic strategy, so far most studies have investigated the to mice intraperitoneally (ip) in a volume of 1 mL per 100 Drug Design, Development and Therapy downloaded from https://www.dovepress.com/ by 54.70.40.11 on 28-Apr-2018 effects of acute DHEAS treatment.15 Moreover, despite the g body weight. In the acute experiments, 10 mg/kg DHEAS knowledge that susceptibility to various mental disorders, or saline was given 30 minutes prior to the animal testing. including the sensitivity to seizures,52 as well as association In the chronic experiments, mice were treated with DHEAS between DHEAS and different health outcomes,53 often differ (10 mg/kg) or saline once daily for 4 consecutive weeks. The by sex, most preclinical studies of DHEAS were performed DHEAS dose was selected according to the literature data only in males. reporting that in mice, concentrations of dehydroepiandroster- Hence, given the
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