Epileptogenic agents enhance transmission at an identified weak electrical synapse in Aplysia

To examine the possibility that alterations in the effectiveness of electrical synapses might participate in epileptogenesis, the effects of several convulsants on an identified weak electrical synapse in Aplysia were examined. Application of pentylenetetrazole, strychnine, or tetraethylammonium led to a dramatic increase in the size of the electrical postsynaptic potential mediated by the synapse; penicillin was considerably less effective. In a number of animals, the increased electrical synaptic effectiveness led to the abnormal conduction of spikes across the synapse. If convulsants have a similar action in mammalian cortex, enhanced transmission at weak electrical synapses may provide abnormal pathways for the flow of seizure activity and contribute in part to the synchronous firing of neurons characteristic of epileptic activity.