Characterization of acute neurotoxic effects of trimethylolpropane phosphate via neuronal network biosensors

We have utilized cultured neuronal networks grown on microelectrode arrays to demonstrate rapid, reliable detection of a toxic compound, trimethylolpr opane phosphate (TMPP). Initial experiments. which were performed blind. de monstrated rapid classification of the compound as a convulsant. a finding consistent with previous whole animal neurobehavioral studies. TMPP (2-200 muM) reorganized network spike activity into synchronous, quasi-periodic bu rst episodes. Integrated burst amplitudes invariably increased, reflecting higher spike frequencies within each burst. The variability of network burs t parameters, quantified as coefficients of variation (CVs), was decreased. Mean CVs for burst duration, interburst interval, and burst rate were lowe red by 42 +/- 13, 58 +/- 5.5, and 62 +/- 1.8%, respectively (mean SEM, n = 8 cultures, 197 channels). These changes in network activity paralleled the effects induced by bicuculline, a known disinhibitory and seizure-inducing drug, and confirmed classification of TMPP as a potential epileptogenic co mpound. Simple pharmacological tests permit exploration of mechanisms under lying observed activity shifts. The EC50 for GABA inhibition of network act ivity was increased from 2.8 to 7.0 muM by 20 muM TMPP and to 20.5 muM by 2 00 muM TMPP. Parallel dose-response curves suggest that TMPP acts by a comp etitive antagonism of GABA inhibition, and are consistent with reported pat ch-clamp analysis of TMPP-induced reduction of inhibitory postsynaptic curr ent amplitudes. The potency of TMPP in generating epileptiform activity in vitro was comparable to concentrations reported for in vivo studies. TMPP a nd bicuculline produced both increases and decreases in burst rate dependin g on native spontaneous bursting levels. These results demonstrate a need f or multivariate analysis of network activity changes to yield accurate pred ictions of compound effects. (C) 2001 Elsevier Science B.V. All rights rese rved.