The long term goal is to understand the cellular mechanisms underlying epileptiform activity. the immediate strategy is to apply patch clamp techniques to the study of ion conductances that are likely to be important in epilepsy to determine (1) the normal characteristics of these conductances and (2) modulation of these conductances by neurotransmitters and intracellular mediators. Understanding the modulation of neuronal conductances by metabolic state may provide clues regarding the paroxysmal nature of seizures. Calcium currents may have multiple roles in seizure activity. Initial studies will use bullfrog sympathetic neurons as a model system for study of calcium current and its modulation by phosphorylation. Phosphatase inhibitors profoundly enhanced the rate of N-calcium current inactivation in preliminary experiments, an action blocked by non-specific protein kinase inhibitors. Additional studies will investigate kinetic and biochemical mechanisms by which phosphatase inhibitors affect inactivation. this will be followed by development of acutely dissociated rat thalamic neurons for patch clamp study. Thalamic neurons were chosen for their role in driving the 3 Hz spike and wave cortical rhythm in absence (petit mal) seizures. Thalamic neurons exhibit oscillatory behavior both during sleep and in vitro while synaptic transmission is blocked. There is evidence that this rhythmic pattern of activity is linked to absence seizures. The role of calcium and other conductances in generating the intrinsic oscillatory behavior of thalamic neurons will be studied. Kinetic models of these conductances will be developed to construct a computer model of the oscillatory behavior. The model will be tested by comparing patterns of oscillations generated by the model with the actual activity produced by thalamic neurons. Finally, the influence of neurotransmitters and intracellular mediators on thalamic oscillatory behavior will be studied.