Spontaneous versus elicited seizures following ethanol withdrawal: differential time course

Ethanol withdrawal symptoms in clinical populations are observed to occur in unique clusters which differ in time of onset relative to the time of withdrawal and in their duration. Since periods of mild symptoms are sometimes observed between these clusters of more severe symptoms, the symptom clusters may reflect separate periods of hyperexcitability during which times different neuronal mechanisms are involved. To investigate this possibility in an animal model of ethanol withdrawal, rats were chronically exposed to ethanol in vapor inhalation chambers. Upon withdrawal from this exposure regimen, the time course of spontaneous seizure activity was observed for a period of 84 hr and compared to sensitivity to seizures elicited by audiogenic stimuli or by the convulsant drug picrotoxin. Spontaneous seizure events were observed to occur in clusters, and these clusters were differentially correlated with periods of increased sensitivity to induced seizure activity. These results further support the suggestion that seizure sensitivity during ethanol withdrawal may indicate the involvement of multiple, independent, neuronal mechanisms.