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Cellular interactions in the rat somatosensory thalamocortical system during normal and epileptic 5–9 Hz oscillations
Author(s) -
Pinault Didier
Publication year - 2003
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.2003.046573
Subject(s) - reticular connective tissue , neuroscience , depolarization , somatosensory system , excitatory postsynaptic potential , reticular activating system , thalamus , intracellular , reticular formation , physics , chemistry , biology , biophysics , anatomy , stimulation , microbiology and biotechnology , inhibitory postsynaptic potential
In Genetic Absence Epilepsy Rats from Strasbourg (GAERS), generalized spike‐and‐wave (SW) discharges (5–9 SW s −1 ) develop during quiet immobile wakefulness from a natural, medium‐voltage, 5–9 Hz rhythm. This study examines the spatio‐temporal dynamics of cellular interactions in the somatosensory thalamocortical system underlying the generation of normal and epileptic 5–9 Hz oscillations. Paired single‐unit and multi‐unit recordings between the principal elements of this circuit and intracellular recordings of thalamic, relay and reticular, neurones were conducted in neuroleptanalgesied GAERS and control, non‐epileptic, rats. The identity of the recorded neurones was established following juxtacellular or intracellular marking. At least six major findings have emerged from this study. (1) In GAERS, generalized spike‐and‐wave discharges were correlated with synchronous rhythmic firings in related thalamic relay and reticular neurones. (2) Usually, corticothalamic discharges phase‐led related relay and reticular firings. (3) A depolarizing wave emerging from a barrage of EPSPs was the cause of both relay and reticular discharges. (4) In some relay cells, which had a relatively high membrane input resistance, the depolarizing wave had the shape of a ramp, which could trigger a low‐threshold Ca 2+ spike. (5) In reticular cells, the EPSP barrage could further trigger voltage‐dependent depolarizations. (6) The epilepsy‐related thalamic, relay and reticular, intracellular activities were similar to the normal‐related thalamic activities. Overall, these findings strongly suggest that, during absence seizures, corticothalamic neurones play a primary role in the synchronized excitation of thalamic relay and reticular neurones. The present study further suggests that absence‐related spike‐and‐wave discharges correspond to hypersynchronous wake‐related physiological oscillations.