Introduction: Gene expression regulation is essential for correct functioning of the cell. Complex processes such as development, apoptosis, cell differentiation, and cell cycling require a fine tuning of gene expression. microRNAs (miRNAs) are small RNAs that have been recognized as key components of the gene expression regulatory machinery. microRNAs are a class of small RNA regulators that are involved in numerous cellular processes, including development, proliferation, differentiation, neurogenesis, and plasticity. miRNAs are critical contributors to the regulation of gene expression in the nervous system. Conclusion: Emerging evidence indicates that microRNAs regulate both the development and function of the nervous system. Deficiency in microRNA function has also been implicated in a number of neurological disorders. Understanding the roles of microRNAs will provide new insights into the complexity and operation of the nervous system.

Introduction: Discovering the enzymes involved in steroid biosynthesis in the central nervous system and the ability of neurons and glial cells to produce steroids is one of the major findings of neurobiology over the last two decades. Unlike classical steroids, these neurosteroids influence neuronal function through direct interactions with neurotransmitter receptors at the cell surface. Conclusion: Extensive studies have shown diverse physiological and pharmacological effects for these compounds. Moreover, neurosteroids have been shown to be involved in different pathological procedures, including neurodegenerative and neuro inflammatory disorders as well as neuropsychiatric diseases. Herein, we will review different aspects of neurosteroid biosynthesis and functions as well as their involvement in the pathogenesis of brain diseases.