The effects of chronic ethanol administration on amygdala neuronal firing and ethanol withdrawal seizures.

Physical dependence on ethanol results in an ethanol withdrawal (ETX) syndrome including susceptibility to audiogenic seizures (AGS) in rodents after abrupt cessation of ethanol. Chronic ethanol administration and ETX induce functional changes of neurons in several brain regions, including the amygdala. Amygdala neurons are requisite elements of the neuronal network subserving AGS propagation during ETX induced by a subacute "binge" ethanol administration protocol. However, the effects of chronic ethanol administration on amygdala neuronal firing and ETX seizure behaviors are unknown. In the present study ethanol (5g/kg) was administered intragastrically in Sprague-Dawley rats once daily for 28days [chronic intermittent ethanol (CIE) protocol]. One week later the rats began receiving ethanol intragastrically three times daily for 4days (binge protocol). Microwire electrodes were implanted prior to CIE or on the day after CIE ended to record extracellular action potentials in lateral amygdala (LAMG) neurons. The first dose of ethanol administered in the binge protocol following CIE treatment did not alter LAMG neuronal firing, which contrasts with firing suppression seen previously in the binge protocol alone. These data indicate that CIE induces neuroadaptive changes in the ETX network which reduce LAMG response to ethanol. LAMG neuronal responses to acoustic stimuli prior to AGS were significantly decreased during ETX as compared to those before ethanol treatment. LAMG neurons fired tonically throughout the tonic convulsions during AGS. CIE plus binge treatment resulted in a significantly greater mean seizure duration and a significantly elevated incidence of death than was seen previously with the binge protocol alone, indicating an elevated seizure severity following chronic ethanol administration.