Cocaine and pseudococaine: comparative effects on electrical after-discharge in the limbic system of cats

The effects of cocaine and its dextroisomer pseudococaine on electrical after-discharge (AD) evoked by electrical stimulation of the hippocampus or amygdala were studied in cats with electrodes implanted in the brain. Intravenous injection of cocaine (2.0 to 4.0 mg/kg doses) produced a suppressive effect on the AD while producing low-voltage fast waves (LVFWs) in the electrical activities of the brain (EEG) associated with behavioral excitation. In contrast, pseudococaine at the same dose as cocaine failed to show a significant suppressive effect on the AD except at high doses (5.0 mg/kg). Pseudococaine produced high-voltage slow waves (HVSWs) in the EEG associated with behavioral depression. A linear dose-response relationship was observed for the suppressive effect of cocaine on the AD. The results suggested that the limbic system may be involved as a primary site of action of cocaine in the central nervous system (CNS).