In vitro evaluation of pyrethroid-mediated changes on neuronal burst parameters using microelectrode arrays

Effects of pyrethroids (beta-cyfluthrin, bifenthrin, cypermethrin, deltamethrin, lambda-cyhalothrin, and permethrin) on the burst parameters (mean burst rate [MBR], percent spikes in burst [PSB], mean burst duration [MBD], mean spikes in burst [MSB], mean interspike interval in burst [MISIB], and mean interburst interval [MIBI]) have been investigated using the microelectrode array technique. Rat cortical neuronal networks (between 24 and 35 DIV) were exposed to the five accumulative concentrations of pyrethroids (0.01μM, 0.1μM, 1μM, 10μM, and 100μM) after initially recording the baseline activity. When compared to the baseline, the burst parameter that had undergone the most change (either increase/decrease) at the initial concentrations was MBR, followed by MIBI and PSB. The other burst parameters (MSB, MBD, and MISIB) did not undergo much change (either increase/decrease) by the pyrethroids at the initial concentrations when compared to the baseline. The MBR of all pyrethroids rose at initial concentrations followed by decrease at higher concentrations. A drop in the MIBI accompanied the rise in the MBR. The rank orders of relative potency of pyrethroids on the IC₅₀ of different burst parameters clearly distinguish type-1 pyrethroids (bifenthrin, permethrin) from the type-2 pyrethroids (beta-cyfluthrin, cypermethrin, deltamethrin, lambda-cyhalothrin), with type-2 being more potent. The rank order of relative potency of pyrethroids based on the IC₅₀ of MBR was beta-cyfluthrin>lambda-cyhalothrin>deltamethrin>cypermethrin>bifenthrin>permethrin.