Effects of antidepressants and related drugs on the quantitatively analyzed EEGs of beagles

Abstract

AbstractPower spectral analysis was applied to beagles' EEGs to determine if clinically effective antidepressants produce changes different from those produced by related drugs. Bipolar EEGs were recorded from screws chronically implanted in the skull 5 mm anterior and 10 mm posterior to bregma, 4 mm left of midline. The normalized spectral estimates obtained after intravenous drug injection (minus the temporally corresponding spectral estimates after saline) were averaged across dogs. Drug effects were related to dose and time. Reliable effects of imipramine, amitriptyline, desipramine, and mianserin were an increase in the percent of power in the 4.5–7.5 Hz (theta) band, an increased percent of power in the alpha band at low doses, a decreased percent of power above 22 Hz (beta‐2), and an increased total spectral absolute power, at doses that produced no symptoms. Chlorpromazine's EEG effects were similar to the antidepressants'. Atropine increased percent theta and decreased percent beta‐1 and beta‐2, but was distinguished from the above drugs since it also increased percent delta and produced symptoms at the lowest effective dose. The other drugs either had no effect on percent theta (physostigmine) or decreased it (chlordiazepoxide, dextroamphetamine, and cocaine); cocaine increased only percent delta. Chlordiazepoxide, dextroamphetamine, and physostigmine increased percent beta‐1 and/or beta‐2, and they either decreased total power (dextroamphetamine) or produced no change in this parameter, and thus were distinguished from antidepressants. The results support the conclusion that antidepressants have distinct acute effects on brain electrical activity, and suggest that novel antidepressants can be detected by EEG spectral analysis in dogs.