Effect of tricyclic antidepressants on the Somatosensory evoked potential in man

The effect of orally administered single doses of placebo, imipramine and amitriptyline on the human Somatosensory evoked potential (SEP) was investigated in three matched groups of 10 male normal volunteers each. In contrast to placebo, the two antidepressants induced characteristic and systematic changes in the evoked response: imipramine as well as amitriptyline decreased the latency in the first three SEP peaks, but increased the latency in the subsequent peaks. The amplitudes were attenuated (especially in the latter part of the response) with the exception of peaks 3–4. The drug profiles seem to be characteristic for tricyclic antidepressants and differ appreciably from those of major tranquilizers, minor tranquilizers and stimulants. Interestingly, the latency decrease was significantly greater after imipramine than after amitriptyline, while the latency increase was more marked after amitriptyline than after imipramine. In addition, the former drug produced more amplitude attenuation than the latter. This indicates that of the two antidepressants, amitriptyline has more sedative properties, whereas imipramine has more stimulatory qualities. Based on these findings as well as on our past experiences with representatives of other psychopharmacological classes, it was concluded that the SEP technique in conjunction with quantitative and statistical evaluation methods seems to be a promising tool for the classification of psychotropic agents.