The current study presents an organotypic rat midbrain slice culture that served as a consistent and informative framework, where the STN neurons and their interconnectivity were closely examined with respect to electrophysiological and pharmacological properties. From multi-electrode array recordings, it was found that the majority of STN neurons spontaneously fired in bursts rather than tonically under control conditions, and the neural activity between pairs of burst-firing STN neurons was tightly correlated. This spontaneous synchronized burst firing was also affected by a glutamate receptor antagonist, yet unaffected by a GABA receptor antagonist. Moreover, even when the STN was isolated from all its known external inputs, spontaneous synchronized burst firing was still observed under control conditions and consistently switched to tonic firing following the application of a glutamate receptor antagonist. Therefore, the results indicated the existence of glutamatergic projections to the STN in the slice preparation, and these excitatory synaptic connections appeared to originate from axon collaterals within the STN rather than other basal ganglia nuclei. It could be concluded that the STN neurons and their interconnectivity are essential requirements in the rat brain slice preparation to produce spontaneous synchronized burst firing.
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