How manipulating the excitatory-inhibitory balance within in vitro neuronal networks with dopamine impacts network dynamics

Neuronal oscillations take place within both cortical and hippocampal circuits and particular frequencies have been associated with cognitive processes such as working memory and attention. These oscillations manifest due to the synchronized activity within neural populations and the underlying neural spiking and bursting between individual cells is modulated by changes in intrinsic membrane excitability and synaptic transmission. The effects of dopamine - a neuromodulator known to impact learning, memory and attention - on synchronized activity has been widely studied in neural regions such as prefrontal cortex and striatum but fewer studies have investigated how dopamine impacts membrane excitability and network dynamics within the hippocampus, the neural region involved in spatial working memory. We use a 64-channel microelectrode array system to record extracellular action potential activity to study how dopamine modulates neuronal network activity from cultured hippocampal neurons. We find that while application of dopamine increases network and synchronized activity, the increase is short-lived with a return to basal levels. However, we show that upon an extended incubation with dopamine followed by application of glutamate, an excitatory neurotransmitter, network activity is increased over a longer timescale than with dopamine alone and we identify the receptor subtype that might play a role in this activity.