en Clinical Neuroscience Clinical Neuroscience Original Original <p style="text-align: justify;"><strong>Introduction: </strong>According to the cumulative evidence, genes encoding GABA receptors inhibit neurotransmitters in CNS and are intricately involved in the pathogenesis of mood disorders. Based on this hypothesis, these genes may be expressed in bipolar patients. As a result, we evaluated the gene expressions of GABA-&beta;3 and HT1D receptors to assess their associations with bipolar mood disorder.&nbsp;<br> <strong>Methods: </strong>In this study, 22 patients with bipolar I disorder (single manic episode) and 22 healthy individuals were enrolled. All participants were older than 15 years and had referred to Farshchian Hospital, Hamadan, Iran. They were diagnosed based on DSM IV&ndash;TR criteria and young mania rating scale in order to determine the severity of mania by a psychiatrist as bipolar Type 1 disorder in manic episode.&nbsp; We evaluated the expression of GABA&ndash;&beta;3 and HT1D receptor genes in peripheral blood mononuclear cells, using&nbsp; real-time RT-PCR analysis.<br> <strong>Results:</strong> In our study, a reduction in the gene expression of GABA&ndash;&beta;3 and HT1D receptors was observed in peripheral blood mononuclear cells of the patients with bipolar disorders compared to the healthy controls.<br> <strong>Conclusion:</strong> The results of this study supports the hypothesis that the gene expression for serotonin and GABA receptors can be employed&nbsp; in elucidating the pathogenesis of bipolar disorders.</p> GABA-β3, HT1D, Serotonin, Bipolar disorder, Gene expression 129 134 http://bcn.iums.ac.ir/browse.php?a_code=A-10-976-1&slc_lang=en&sid=1 Mohammadreza Moradi moradiava@gmail.com 13700319475328460015553 13700319475328460015553 No Molecular Medicine Research Center, Hamadan University of Medical Sciences, Hamadan, Iran. Massoud Saidijam sjam110@yahoo.com 13700319475328460015554 13700319475328460015554 No Molecular Medicine Research Center, Hamadan University of Medical Sciences, Hamadan, Iran. Reza Yadegarazari reza.yadegarazari@yahoo.com 13700319475328460015555 13700319475328460015555 No Molecular Medicine Research Center, Hamadan University of Medical Sciences, Hamadan, Iran. Leila Jahangard Jahangard_Li@yahoo.com 13700319475328460015556 13700319475328460015556 No Behavioral Disorders and Substance Abuse Research Center, Hamadan University of Medical Sciences, Hamadan, Iran. Maryam Seifi seifi142@gmail.com 13700319475328460015557 13700319475328460015557 No Molecular Medicine Research Center, Hamadan University of Medical Sciences, Hamadan, Iran. Nasrin Matinnia nmatinnia@yahoo.com 13700319475328460015558 13700319475328460015558 No Department of Nursing, Faculty of Science, Hamadan Branch, Islamic Azad University, Hamadan, Iran. Ali Ghaleiha dralighaleiha@gmail.com 13700319475328460015559 13700319475328460015559 Yes Behavioral Disorders and Substance Abuse Research Center, Hamadan University of Medical Sciences, Hamadan, Iran.