Changes in intracellular calcium transients and LTP in the surround of visual cortex lesions in rats.
Injury and loss of neurons are observed in the center of a cerebral cortical lesion. Mechanisms of early functional reorganization post-lesion involve changes in the strength of synaptic coupling as measured in long-term potentiation (LTP). Since these changes in LTP may depend on the intraneuronal calcium concentration ([Ca2+]I), the present study analyzed the strength of synaptic LTP combined with measurements of the stimulus-induced peak calcium influx in slices from rat visual cortex in vitro. Slices were analyzed 1-7 days post-lesion by use of electrophysiological and calcium fluorescence imaging techniques. A theta-burst stimulus (TBS) was electrically applied to cortical layer IV, while changes in extracellular field potentials (FPs) and in the corresponding peak calcium influx were recorded in layers II/III. Both the strength of LTP and of the FP mediated peak calcium influx were significantly enhanced 1-6 days post-lesion at a distance of 4 mm from the lesion border. Pharmacological experiments revealed that the expression of LTP was dependent on the activation of NMDA receptors. The area of increased stimulus-evoked peak calcium influx correlated with the enhanced LTP, suggesting that changes in [Ca2+]I mediate the strength of long-term synaptic plasticity following a cortical lesion. This mechanism may support synaptic reorganization in the surround of the deafferented region in rat visual cortex.
Barmashenko
G
G
Department of Neurobiology, Ruhr-University Bochum, D-44780, Bochum, Germany.
Eysel
U T
UT
Mittmann
T
T
D015763:2-Amino-5-phosphonovalerate / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology*; D002138:Calibration; D004558:Electric Stimulation; D004594:Electrophysiology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D005110:Extracellular Space / Q000502:physiology; D005456:Fluorescent Dyes; D016257:Fura-2; D066298:In Vitro Techniques; D007834:Lasers; D017774:Long-Term Potentiation / Q000187:drug effects / Q000502:physiology*; D008564:Membrane Potentials / Q000502:physiology; D008856:Microscopy, Fluorescence; D051381:Rats; D016194:Receptors, N-Methyl-D-Aspartate / Q000037:antagonists & inhibitors; D014793:Visual Cortex / Q000293:injuries / Q000473:pathology* / Q000503:physiopathology
D018691:Excitatory Amino Acid Antagonists; D005456:Fluorescent Dyes; D016194:Receptors, N-Methyl-D-Aspartate; D015763:2-Amino-5-phosphonovalerate; D002118:Calcium; D016257:Fura-2