Vol.:(0123456789) 1 3 Cellular and Molecular Neurobiology (2019) 39:471–472 https://doi.org/10.1007/s10571-019-00657-9 EDITORIAL Introduction to the Special Issue “Neuroactive Steroids” Alejandro F. De Nicola 1,2  · Maria Claudia Gonzalez Deniselle 1,3 Received: 23 January 2019 / Accepted: 29 January 2019 / Published online: 2 April 2019 © Springer Science+Business Media, LLC, part of Springer Nature 2019 Abstract Steroids are complex molecules, exerting known and still unknown efects in the nervous system. Throughout this volume, the reader will fnd a wide spectrum of articles, giving an up-to-date account of the molecular, physiological, pharmacologi- cal, and clinical aspects of steroid action on the nervous system. Keywords Progesterone · Mineralocortiod receptors · Glucocorticoid receptors · Mifepristone · Neuroactive steroids · Neuropathology Introduction We would like to start this Introduction by quoting Hans Selye’s words (Selye 1947): “The manifold pharmacological activities of the steroids and the fact that almost any of them possess an apparently unpredictable combination of such activities tend to give the impression of a complete lack of orderliness”. This thematic statement of despair was later moderated in the same textbook: “This type of study (refer- ring to steroid efects) is perhaps the most fascinating and, from the practical point of view, the most important aspect of contemporary steroid hormone research”. Stunning words from a man that ahead of his time, revealed the complex world of the steroid feld. The idea for gathering new devel- opments on the topic of steroids and nervous system started during an informal café chat with Dr. Juan Maria Saavedra in Buenos Aires. He asked Maria Claudia and me to con- sider being the editors of a Special Issue on Neuroactive Steroids, to be published in Cellular and Molecular Neuro- biology. We thought it was a big challenge, considering the ever-changing cellular and molecular mechanisms appearing in this area of neuroendocrinology. Nevertheless, the chal- lenge was accepted and in the next months we invited top investigators in the steroid feld to contribute to this Spe- cial Issue. Throughout the volume, the reader will fnd a wide spectrum of articles, giving an up-to-date account of the physiological, pharmacological, clinical, and molecular aspects of steroid action. Nowadays, we know that steroids are complex molecules, exerting known and still unknown efects in the nervous system. Thus, we cannot expect a uni- fed hypothesis to explain what steroids do, but only watch year after year how preconceived concepts crumbled when new and unexpected discoveries arrive. The frst three articles in the Special Issue refer to the efect of progestins. Guennoun et al. (2018) provide evi- dence for the pleiotropic and benefcial efects of progester- one in experimental stroke, highlighting the important role of the progesterone receptor in cerebroprotection. Next, the roles of progesterone and its reduced metabolite allopreg- nanolone are discussed by Gonzalez et al. (2018). These authors explored in their review how these compounds pre- vent or reverse the maladaptive changes of pain behavior arising after injury or disease. A third article concerns with aromatase, an enzyme metabolizing androgens into estro- gens, Brocca and Garcia-Segura (2018) describe the non- reproductive efects of aromatase in the brain, and discuss how brain aromatase is involved in cognition and mood. In pathological conditions, however, this enzyme partici- pates in a reparative response and ofers neuroprotection, by increasing the levels of neural-derived estradiol. * Alejandro F. De Nicola alejandrodenicola@ibyme.conicet.gov.ar 1 Laboratory of Neuroendocrine Biochemistry, Instituto de Biologia y Medicina Experimental, Obligado 2490, 1428 Buenos Aires, Argentina 2 Department of Human Biochemistry, Faculty of Medicine, University of Buenos Aires, Paraguay 2155, 1121 Buenos Aires, Argentina 3 Department of Physiological Sciences, Faculty of Medicine, University of Buenos Aires, Paraguay 2155, 1121 Buenos Aires, Argentina