Spindle-like thalamocortical synchronization in a rat brain slice preparation.
We obtained rat brain slices (550-650 microm) that contained part of the frontoparietal cortex along with a portion of the thalamic ventrobasal complex (VB) and of the reticular nucleus (RTN). Maintained reciprocal thalamocortical connectivity was demonstrated by VB stimulation, which elicited orthodromic and antidromic responses in the cortex, along with re-entry of thalamocortical firing originating in VB neurons excited by cortical output activity. In addition, orthodromic responses were recorded in VB and RTN following stimuli delivered in the cortex. Spontaneous and stimulus-induced coherent rhythmic oscillations (duration = 0.4-3.5 s; frequency = 9-16 Hz) occurred in cortex, VB, and RTN during application of medium containing low concentrations of the K(+) channel blocker 4-aminopyridine (0.5-1 microM). This activity, which resembled electroencephalograph (EEG) spindles recorded in vivo, disappeared in both cortex and thalamus during application of the excitatory amino acid receptor antagonist kynurenic acid in VB (n = 6). By contrast, cortical application of kynurenic acid (n = 4) abolished spindle-like oscillations at this site, but not those recorded in VB, where their frequency was higher than under control conditions. Our findings demonstrate the preservation of reciprocally interconnected cortical and thalamic neuron networks that generate thalamocortical spindle-like oscillations in an in vitro rat brain slice. As shown in intact animals, these oscillations originate in the thalamus where they are presumably caused by interactions between RTN and VB neurons. We propose that this preparation may help to analyze thalamocortical synchronization and to understand the physiopathogenesis of absence attacks.
Dipartimento di Neuroscienze, Università degli Studi di Roma Tor Vergata, 00173 Rome, Italy.
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Tancredi
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Biagini
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D'Antuono
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Louvel
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Pumain
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Avoli
D015761:4-Aminopyridine / Q000494:pharmacology*; D000818:Animals; D001463:Barbiturates / Q000494:pharmacology; D002540:Cerebral Cortex / Q000166:cytology* / Q000502:physiology*; D003344:Cortical Synchronization / Q000187:drug effects*; D004558:Electric Stimulation; D004827:Epilepsy / Q000139:chemically induced / Q000503:physiopathology; D004832:Epilepsy, Absence / Q000139:chemically induced / Q000503:physiopathology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D066298:In Vitro Techniques; D007736:Kynurenic Acid / Q000494:pharmacology; D009434:Neural Pathways; D010507:Periodicity; D051381:Rats; D017208:Rats, Wistar; D011930:Reaction Time / Q000502:physiology; D012894:Sleep Stages / Q000502:physiology; D013788:Thalamus / Q000166:cytology* / Q000502:physiology*
D001463:Barbiturates; D018691:Excitatory Amino Acid Antagonists; D015761:4-Aminopyridine; D007736:Kynurenic Acid; C032232:barbituric acid