Abstract
The author and colleagues have previously reported the decrease in the amplitude-ratio of P100 of visual evoked potentials (VEP) after overloading mental tasks in unmedicated patients with endogenous depression and the increase in the amplitude-ratio after the tasks during treatment with tricyclic anti-depressants. In the present study the relationships between this amplitude-ratio increase and the dose, the severity of the illness and factors relating to the time course during the treatment of imipramine were investigated in 20 patients with endogenous depression.
VEP was recorded 3-5 times before the treatment and every week during the treatment. The severity of the illness was estimated by the Hamilton Rating Scale at each time point of VEP recording. As overloading mental tasks a modification of Kadobayashi's addition task method was used.
The results were as follows:
1) There was no significant correlation between the time course of the treatment and the increase of the amplitude-ratio of VEP during the treatment.
2) The amplitude-ratio increase depended on the dose of imipramine. On a dose of more than 75 mg/day a significant increase in the amplitude-ratio was observed compared with that in doses below 75 mg/day (p<0.01).
3) No correlations were seen between the amplitude-ratio or the amplitude-ratio change and the severity of the illness before and during the treatment.
From these results it might be concluded that the increase in the amplitude-ratio of P100 of VEP after the mental tasks was not brought about by the changes in the severity of the illness or factors relating to the time course of the treatment, but by the direct effect of imipramine to the patient's brain or the physiological changes caused by the drug.
