PT - JOURNAL ARTICLE AU - Zhengyu Cao AU - Xiaohan Zou AU - Yanjun Cui AU - Susan C Hulsizer AU - Pamela J Lein AU - Heike Wulff AU - Isaac N. Pessah TI - Rapid Throughput Analysis Demonstrates that Chemicals with Distinct Seizurogenic Mechanisms Differentially Alter Ca<sup>2+</sup> Dynamics in Networks Formed by Hippocampal Neurons in Culture AID - 10.1124/mol.114.096701 DP - 2015 Jan 01 TA - Molecular Pharmacology PG - mol.114.096701 4099 - http://molpharm.aspetjournals.org/content/early/2015/01/12/mol.114.096701.short 4100 - http://molpharm.aspetjournals.org/content/early/2015/01/12/mol.114.096701.full AB - Primary cultured hippocampal neurons (HN) form functional networks displaying synchronous Ca2+ oscillations (SCOs) whose patterns influence plasticity. Whether chemicals with distinct seizurogenic mechanisms differentially alter SCO patterns was investigated using mouse HN loaded with the Ca2+ indicator fluo-4-AM. Intracellular Ca2+ dynamics were recorded from 96-wells simultaneously in real-time using Fluorescent Imaging Plate Reader (FLIPR®). Although quiescent at 4 DIV, HN acquired distinctive SCO patterns as they matured to form extensive dendritic networks by 16 DIV. Challenge with kainate, a kainate receptor (KAR) agonist, 4-aminopyridine (4-AP), a K+ channel blocker, or pilocarpine, a muscarinic acetylcholine receptor agonist caused distinct changes in SCO dynamics. Kainate at &lt;1μM produced a rapid rise in baseline Ca2+ (Phase I Response) associated with high frequency and low amplitude SCOs (Phase II Response), whereas SCOs were completely repressed with &gt;1μM kainate. KAR competitive antagonist CNQX (1-10μM) normalized Ca2+ dynamics to the pre-kainate pattern. Pilocarpine lacked Phase I activity but caused a 7-fold prolongation of Phase II SCOs without altering either their frequency or amplitude, an effect normalized by atropine (0.3-1μM). 4-AP (1-30μM) elicited a delayed Phase I response associated with persistent high frequency, low amplitude SCOs, and these disturbances were mitigated by pretreatment with the KCa activator SKA-31. Consistent with its antiepileptic and neuroprotective activities, non-selective voltage-gated Na+ and Ca2+ channel blocker lamotrigine partially resolved kainate- and pilocarpine-induced Ca2+ dysregulation. This rapid throughput approach can discriminate among distinct seizurogenic mechanisms that alter Ca2+ dynamics in neuronal networks and may be useful in screening anti-epileptic drug candidates.