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Neural dynamics in cortex-striatum co-cultures--II. Spatiotemporal characteristics of neuronal activity.
Plenz D, Aertsen A.
Max-Planck-Institut fur biologische Kybernetik, Tubingen, Germany.
dynamics in organotypic cortex-striatum co-cultures grown for three to
six weeks under conditions of dopamine deficiency are described. Single
neuron activities were recorded intra- and extracellularly, and
spatiotemporal spreading of population activity was mapped using
voltage-sensitive dyes. The temporal properties of spike firing were
characterized by interspike interval histograms, autocorrelation and
crosscorrelation. Cortical pyramidal neurons (n = 40) showed irregular
firing with a weak tendency to burst or to oscillate. Crosscorrelations
revealed strong near-coincident firing and synaptic interactions.
Disinhibition was a notable feature in a strongly firing cortical
interneuron. Cortical activity spread in the co-culture, thus inducing
an overall, homogeneous depolarization in the striatal part. Striatal
cells were divided into principal cells and type I and II secondary
cells. Principal cells (n = 40) were similar to those reported
previously in vivo. Spiking activity ranged from irregular spiking at
very low rates to episodic bursting, with an average burst duration of
1 s. Interspike intervals were single-peaked. Intracellular recordings
revealed characteristic, long-lasting subthreshold depolarizations
("enabled state") that were shortened by local muscarinic receptor
blockade. During prolonged time periods in the "enabled state", locally
applied bicuculline induced strong firing in most principal neurons.
Striatal secondary type I neurons (n = 25) showed high spiking rates,
single- and double-peaked interval histograms and low-threshold,
short-lasting stereotyped bursting activity and occasional rhythmic
bursting. The firing of these neurons was increased by bicuculline.
Crosscorrelations showed synchronization of these cells with principal
cell activity. Secondary type II neurons (n = 15) revealed tonic,
irregular firing patterns similar to cortical neurons, except with
occasional firing in doublet spikes. We conclude that under conditions
of dopamine deficiency in corticostriatal co-cultures (i) the cortex
induces the "enabled" state and typical bursting mode in striatal
principal neurons; (ii) principal neurons are strongly inhibited during
the "enabled" state; (iii) muscarinic activity, presumably from
tonically active striatal cholinergic interneurons, stabilizes the
"enabled" state; (iv) striatal GABAergic interneurons receives synaptic
inhibition and take part in synchronized activity among striatal
principal cells. Our results favor the view of the striatum as a
lateral inhibition network.
PMID: 8848173 [PubMed - indexed for MEDLINE]