Blockade of 5-HT3 receptor with MDL7222 and Y25130 reduces hydrogen peroxide-induced neurotoxicity in cultured rat cortical cells

The present study was performed to examine the neuroprotective effects of 5-hydroxytryptamine (5-HT)3 receptor antagonists against hydrogen peroxide (H2O2)-induced neurotoxicity using cultured rat cortical neurons. Pretreatment of 5-HT3 receptor antagonists, tropanyl-3,5-dichlorobenzoate (MDL72222, 0.1 and 1 μM) and N-(1-azabicyclo[2.2.2.]oct-3-yl)-6-chloro-4-ethyl-3-oxo-3,4-dihydro-2H-1,4-benzoxazine-8-carboxamide hydrochloride (Y25130, 0.5 and 5 μM), significantly inhibited the H2O2 (100 μM)-induced neuronal cell death as assessed by a MTT assay and the number of apoptotic nuclei, evidenced by Hoechst 33342 staining. The protective effects of MDL72222 (1 μM) and Y25130 (5 μM) were completely blocked by the simultaneous treatment with 100 μM 1-phenylbiguanide, a 5-HT3 receptor agonist, indicating that the protective effects of these compounds were due to 5-HT3 receptor blockade. In addition, MDL72222 (1 μM) and Y25130 (5 μM) inhibited the H2O2 (100 μM)-induced elevation of cytosolic Ca2+ concentration ([Ca2+]c) and glutamate release, generation of reactive oxygen species (ROS), and caspase-3 activity. These results suggest that the activation of the 5-HT3 receptor may be partially involved in H2O2-induced neurotoxicity, by membrane depolarization for Ca2+ influx. Therefore, the blockade of 5-HT3 receptor with MDL72222 and Y25130 may ameliorate the H2O2-induced neurotoxicity by interfering with the increase of [Ca2+]c, and then by inhibiting glutamate release, generation of ROS and caspase-3 activity.