Interaction between Anxiolytic Effects of Testosterone and β-1 Adrenoceptors of Basolateral Amygdala

Many studies have shown that anxiety-like behaviors are influenced by peripheral and central parameters including hormones and neurotransmitters in the different areas of Central Nervous System (CNS). Many investigations have proven the anxiolytic effect of androgens in different methods. Also, there are many reports about the modulating role of the amygdala complex, especially Basolateral Amygdala (BLA), through adrenergic system on anxiety. Among various types and subtypes of adrenergic receptors, β-1 adrenoceptors (β-1 ARs) of BLA account for the anxiety. The purpose of this study was to examine the relationship between testosterone and β-1 ARs in the BLA as an anxiety regulating key of CNS. Using Elevated plus Maze (EPM), the anxiety-like behaviors of four groups of intact adult male Wistar rat were assessed in the presence of different doses of testosterone (0, 20, 30 and 40 mg kg-1, Intraperitoneal (i.p.). Then, the effects of intra-BLA microinjection of different doses of betaxolol, a selective β-1 ARs antagonist, (0, 0.025, 0.1 and 0.4 μg rat-1), were evaluated in the other four groups. Finally, the interaction between the ineffective dose of testosterone via i.p. and betaxolol via intra-BLA was investigated. The results obtained revealed that testosterone (i.p.) and betaxolol (intra-BLA) alone had anxiolytic effects on the male Wistar rats in a dose-dependent manner. Our findings also showed that the anxiolytic effects of testosterone (i.p.) were reinforced by the intra-BLA injection of betaxolol. Co-administration betaxolol and testosterone also showed the synergistic actions on anxiolytic effects in the adult male Wistar rats. Our results interestingly proposed that the interaction between testosterone and β-1 ARs is in part related to common mechanism and other neurotransmitters include gamma-aminobutyric acid (GABA) and serotonin.