Epileptiform activity in microcultures containing small numbers of hippocampal neurons.

1. Microcultures were grown containing small numbers of hippocampal neurons. The neurons grew on glial cells attached to patches of either collagen or palladium. A layer of agarose underlying the microcultures prevented connections from forming between nearby microcultures. 2. Neurons formed strong chemical synaptic connections within each microculture, with monosynaptic fast-excitatory, fast-inhibitory, and slow-inhibitory synaptic actions. 3. Small networks with as few as two neurons generated epileptiform activity that closely resembled the epileptiform activity seen in mass cultures containing thousands of neurons. The epileptiform activity was observed when microcultures that were grown for weeks in blockers of synaptic activity (kynurenate and elevated Mg2+) were washed free of these blockers. 4. Such a microculture technique allows study of epileptiform activity in a simplified system and facilitates analysis of the synaptic actions underlying the epileptiform activity.