The molecular basis of the abnormal excitability of the kindling phenomenon is unclear. The alterations of neurotransmitters and their receptors identified in this model most likely underlie the brain's response to repetitive neuronal firing during seizures. Cellular localization of neurotransmitter receptor alterations has provided a clue to the network of brain structures responsible for kindling, a necessary first step to elucidating the basic mechanisms. Regardless of whether the molecular basis of kindling involves neurotransmitters per se, study of the role of neurotransmitters should teach many valuable lessons regarding molecular aspects of brain function.