reased reactive oxygen species production. Additionally, Ca2+ activates neuronal nitric oxide synthase and NO produced by this enzyme reacts with superoxide anion forming peroxynitrites, reactive nitrogen species. Together with ROS reactive nitrogen species activate nuclear factor kappa B, a transcriptional regulator of inducible NOS gene, followed by increased production of NO and aggravation of oxidative stress. Other mechanisms of ROS generation include cell swelling, direct effect of Piceatannol ammonia and effects of proinflammatory cytokines. Disturbances in cholinergic transmission as well as changes in acetylcholinesterase activity are associated with HE. Modulation of cholinergic transmission may prevent neurodegeneration and attenuate neuroinflammation, thus suggesting that alterations in cholinergic transmission may contribute to oxidative injury in HE. On the other hand, hyperammonemia synergistically with proinflammatory cytokines in acute HE, and with manganese in chronic HE increases neurosteroid synthesis in astrocytes. Neurosteroids, allopregnanolone and tetrahydro-deoxycorticosterone, potentiate GABAergic transmission through allosteric modulation of GABAA receptor activity and contribute to neuronal inhibition in HE. Central nervous system inhibition by neurosteroids may potentially modulate oxidative stress and cholinergic transmission in the brain, but this effect has not been completely investigated. The possible link between oxidative stress, GABAergic and cholinergic transmission suggests that inhibition of neurosteroid synthesis may modulate oxidative stress and eventually improve the course of HE. Finasteride suppresses neurosteroid synthesis via inhibition of 5-reductase in astrocytic smooth PubMed ID:http://www.ncbi.nlm.nih.gov/pubmed/19757958 endoplasmic reticulum. This effect was found to reduce ethanol intake in mice after development of PubMed ID:http://www.ncbi.nlm.nih.gov/pubmed/19755349 addiction, modulate the emotional state and pain transmission as well as to alter seizure development. Additionally, FIN improves the motor and EEG signs ofthioacetamide -induced HE as well as morphological changes in the liver through incompletely defined mechanisms. The understanding of these mechanisms may contribute to determination 
of potential therapeutical effects of FIN in HE. FIN inhibits ALLO synthesis in the brain, but this effect cannot fully explain its neuroprotective effects, since FIN also inhibits the synthesis of 5-dihydrotestosterone and other steroids. The effects of FIN on oxidative stress and AchE activity in the brain and the contribution of these effects to the course of HE are not elucidated. Based on this background, the aim of our study was to investigate the effects of FIN on oxidative stress and activity of AchE in various brain regions in acute TAA-induced HE in rats. 2 / 14 Finasteride Has Regional Effects in the Brain Materials and Methods Animals Experiments were performed on male adult Wistar rats, weighing 170200 g, that were raised on Military Medical Academy in Belgrade. Animals were kept in individual cages under standard laboratory conditions with free access to pelleted food and tap water. All experimental procedures were in full compliance with Directive of the European Parliament and of the Council and approved by The Ethical Committee of the University of Belgrade. All efforts were made to minimize suffering of animals. All animals were divided into following groups: 1. control, saline and 2-hydroxypropyl-cyclodextrin -treated group; 2. thioacetamide-treated group, TAA; 3. finasteride-treated gr
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