Effects of reduced magnesium on hippocampal synchrony.

Spontaneous, synchronous burst discharges originating in the CA2-CA3 region of guinea pig hippocampal slices occur when the concentration of magnesium in the perfusate is reduced below 250 microM. The burst frequency is greater than that seen with other convulsants and afterdischarge is common. Cyclic periods of bursting resembling ictal discharges occur spontaneously in some slices and with repetitive stimulation (0.5-2 Hz) in most slices. The spontaneous bursts are blocked by 2-APV suggesting the involvement of NMDA receptors in their generation.