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Effects of Conazole Fungicides on Spontaneous Activity in Neural Networks
Citation:
Lynch, B. AND C. Mack. Effects of Conazole Fungicides on Spontaneous Activity in Neural Networks. Society of Toxicology Annual Meeting, New Orleans, LA, March 13 - 17, 2016.
Impact/Purpose:
This work was conducted as part of development of neural networks on microelectrode arrays as a screening tool for neurotoxicity. More directly, it is a student's project that was the result of findings during screening of chemicals in ToxCast using this approach
Description:
Hexaconazole (HEX), Tetraconazole (TET), Fluconazole (FLU), and Triadimefon (TRI) are conazole fungicides, used to control powdery mildews on crops, and as veterinary and clinical treatments. TRI, a demethylation inhibitor, is neurotoxic in vivo, and previous in vitro experiments produced characteristic alterations in neural network mean firing rate (MFR) and bursting patterns measured using microelectrode array (MEA) recordings. Other tested conazoles reduced MFR, but effects on bursting activity were not determined. The present study used 48-well MEA plates to assess effects of FLU, HEX, TET, TRI, and Spiroxamine (SPI, a spiroketal-amine fungicide), on cell viability, MFR, active electrodes (#AE), synchrony (SYNC) and burst parameters (Interburst Interval (IBI), Burst Duration (BD), Burst Frequency (BF), and Number of Bursts (NB)). Primary cortical cell cultures expressed spontaneous electrical activity after 12-15 days in vitro (DIV) in the form of individual spikes and bursts and were tested between DIV 14-34. MFR, bursting and SYNC data were collected, and then analyzed using AxIS 2.1, Axion Biosystems (Atlanta, GA). All compounds were without effect on viability measured by lactate dehydrogenase release and the Cell Titer Blue assay. IC50 values for effects of SPI, TET, HEX and TRI on MFR were 0.44, 0.72, 1.5, and 31µM (n=3), respectively. FLU was without effect on any activity parameter. The remaining fungicides caused similar concentration-dependent decreases in MFR, #AE, burst parameters, and SYNC, with all network activity being completely inhibited at highest concentrations (10-100 µM). In this study, both conazole and amine compounds had neuroactive effects similar to TRI on MFR, and altered bursting characteristics in the neural network. Further investigations are needed to determine the underlying mechanisms by which these chemicals modify cortical network function. (This abstract does not reflect the policies of the United States Environmental Protection Agency)