Ammonium chloride influences in vitro-neuronal network activity

• Published in: Experimental neurology 2012-05, Vol.235 (1), p.368-373
• Main Authors: Schwarz, Clara-Sophie, Ferrea, Stefano, Quasthoff, Kim, Walter, Janine, Görg, Boris, Häussinger, Dieter, Schnitzler, Alfons, Hartung, Hans-Peter, Dihné, Marcel
• Format: Article
• Language: English
• Subjects: 2-Amino-5-phosphonovalerate - pharmacology; Ammonia; Ammonium chloride; Ammonium Chloride - pharmacology; Animals; Biological and medical sciences; Cerebral Cortex - drug effects; Cerebral Cortex - metabolism; Fundamental and applied biological sciences. Psychology; Glutamate-ammonia ligase; Glutamate-Ammonia Ligase - antagonists & inhibitors; Glutamate-Ammonia Ligase - metabolism; Glutamic acid receptors; Glutamine; Glutamine - metabolism; Hepatic encephalopathy; Isolated neuron and nerve. Neuroglia; Medical sciences; Metabolism; Methionine Sulfoximine - pharmacology; Methionine–sulfoximine; Microelectrode recording; Microelectrodes; N-Methyl-D-aspartic acid receptors; Nerve Net - drug effects; Nerve Net - metabolism; Neural networks; Neurology; Neuronal network; Neurons - drug effects; Neurons - metabolism; NMDA-receptor inhibition; Rat; Rats; Receptor mechanisms; Receptors, N-Methyl-D-Aspartate - metabolism; Synapses - drug effects; Synapses - metabolism; Synaptic Transmission - drug effects; Synaptic Transmission - physiology; Synchronization; Vertebrates: nervous system and sense organs
• ISSN: 0014-4886; 1090-2430
• DOI: 10.1016/j.expneurol.2012.02.019

The objective of the present work is to image functional alterations in hepatic encephalopathy (HE) by ammonia-induced changes of in vitro-neuronal network activity and to identify counteracting strategies. Synchronous bursting behavior of rat cortical cells which is the result of synaptic interaction of excitatory and inhibitory neurons was recorded in vitro on microelectrode arrays (MEAs) after ammonium chloride exposure. In order to test the involvement of astrocytic glutamine metabolism and N-methyl-d-aspartic acid- (NMDA-) receptor function in the observed ammonia-induced network dysregulation and to identify potentially protective strategies, we investigated effects of the glutamine synthetase (GS) inhibitor methionine–sulfoximine (MSO) and the NMDA-receptor antagonist DL-2-Amino-5-phosphono-pentanoic acid (AP-5), respectively. We observed a characteristic ammonia-induced increase of global network activity while network synchrony was suppressed. The increase of global activity, but not the suppression of network synchrony was prevented by inhibiting GS. However, blocking NMDA-receptors prevented both, network excitation and desynchronization. Conclusions: 1. The observed desynchronization of in vitro-neuronal network activity after ammonium chloride treatment might reflect global neuronal network changes in HE in vivo and suggests the MEA technology as a valuable tool for measuring changes of neuronal connectivity in vitro. 2. Astrocytic glutamine metabolism might be involved in increased global network activity, but not in the suppression of network synchrony. 3. Overactivation of NMDA-receptors might underlie both, the ammonia-induced increase of activity and suppression of network synchrony, suggesting that NMDA-receptor function is involved in HE and that their blockage might be protective. 4. Measuring neuronal network activity in vitro by the MEA technology might help to describe functionally protective measures in HE. ► Ammonia induces network excitation and desynchronization on microelectrode arrays. ► Astrocytic glutamine metabolism might be involved in network excitation. ► Inhibiting NMDA-receptors protects against network excitation and desynchronization. ► Microelectrode arrays might help to find protective strategies in ammonia toxicity.