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Weak sinusoidal electric fields modify the calcium efflux from freshly isolated chick and cat cerebral tissues bathed in Ringer's solution, at 36 degrees. Following incubation (30 min) with radioactive calcium (45Ca2+), each sample, immersed in fresh solution, was exposed for 20 min to fields at 1, 6, 16, 32, or 75 Hz, with electric gradients of 5, 10, 56,(More)
Calcium (45Ca2+) efflux was studied from preloaded cortex in cats immobilized under local anesthesia, and exposed to a 3.0-mW/cm2 450-MHz field, sinusoidally amplitude modulated at 16 Hz modulation depth 85%). Tissue dosimetry showed a field of 33 V/m in the interhemispheric fissure (rate of energy deposition 0.29 W/kg). Field exposure lasted 60 min. By(More)
Several studies have indicated that weak, extremely-low-frequency (ELF; 1-100 Hz) magnetic fields affect brain electrical activity and memory processes in man and laboratory animals. Our studies sought to determine whether ELF magnetic fields could couple directly with brain tissue and affect neuronal activity in vitro. We used rat hippocampal slices to(More)
Rat hippocampal slices in 0, 0.25, 1.5 or 3 mM penicillin were exposed briefly to extracellular sinusoidal electric fields (20 s, 5 and 60 Hz, 20-40 mV/cm in tissue). Fields induced long-term (min) changes in population spike amplitudes in the CA1 cell layer. Post-field effects included both depression of strongly epileptiform responses and potentiation of(More)
The influence of extracellular sinusoidal electric fields on the amplitude of population spikes evoked by single test pulses in excitatory pathways to CA1 pyramidal neurons was studied in rat hippocampal slices. The fields in the tissue were of the order of EEG gradients. Stimulation at 5 Hz, a frequency representative of hippocampal theta activity, was(More)
The amplitude of population spikes in the CA1 cell layer of rat hippocampal slices was transiently altered during stimulation of the tissue with DC and sinusoidal extracellular electric fields parallel to the dendrosomatic axis of the CA1 pyramidal neurons. Field threshold was about 50 mV/cm in the tissue. Independently, long-lasting (min) increases in(More)
We used combinations of NMDA and quisqualate/kainate (Q/K) receptor antagonists and low Mg2+ (0.1 mM) solutions to study the respective roles of these receptors during in vitro kindling of interictal bursts in the CA3 area of rat hippocampal slices. Intracellular and extracellular recordings in CA3 showed that Q/K receptors were not necessary for the(More)
Weak (20-50 microA) sine-wave stimulation at 60 Hz (SWS) of either the mossy fibers or the Schaffer collaterals promoted epileptiform synchronized bursts in the CA2/3 area of rat hippocampal slices in the absence of epileptogenic agents. Following brief SWSs (2-10 sec every 5 min), delayed synchronized bursts (DSBs) were triggered by weak test pulses in(More)
We investigated the role of nitric oxide (NO) in controlling the rate of occurrence of muscarinic rhythmic slow activity (RSA) episodes induced by carbachol in rat hippocampal slices. Typically, a series of several short intervals (< 40 s) between RSA episodes alternated with one or two longer intervals. Treatments with inhibitors of NO synthesis (NG-nitro-(More)
We previously demonstrated kindling of synchronized bursts (ISs) by repeated sine-wave stimulation (SW: 2-5 sec, 60 Hz, 20-50 microA, every 5 min) in the CA2/3 area of rat hippocampal slices. Here we report the behavior of individual CA2/3 neurons during the kindling procedure. Intra- and extracellular recordings were obtained concurrently before, during(More)