The central effects of atenolol (50 mg tds) and captopril (50 mg tds) ingested for a period of seven days were studied in ten healthy volunteers. A placebo and two active control drugs, methyldopa (250 mg tds) and oxazepam (10 mg), were included in the design. Oxazepam was ingested on the seventh day only, with a placebo being taken on the preceding six days. On the seventh day, central effects of the drugs were tested at 10.00-11.00 h (session 1), immediately before the subjects' last dose of each drug and at 2.5-3.5 h after the final dose of each drug (1330-1430 h, session 2).
Performance was assessed using digit symbol substitution, continuous attention, letter cancellation, choice reaction time, finger tapping, immediate and short-term memory, critical flicker fusion and two flash fusion. Subjects assessed their mood and well-being on a series of 12 visual analogue scales. Recordings of the EEG and body sway were carried out.
Neither atenolol nor captopril altered performance at any of the skills tested. There were no effects on subjectively assessed alertness or mood with captopril, while atenolol significantly increased wakefulness in session 2 and when the two sessions were meaned. Similarly, captopril did not modify body sway, while with atenolol there was a significant decrease in activity in the frequency range 1.0-2.75 Hz from session 1 to session 2. Both captopril and atenolol modified the electrical activity of the brain, with captopril increasing delta and theta activity and atenolol reducing delta, alpha and beta activity.
Methyldopa significantly increased the number of involuntary rest pauses in the finger tapping task, and the choice reaction time from session i to session 2. There was a decrease in passivity during the first session and an increase in wakefulness in session 2 with methyldopa. This drug also decreased body sway in the frequency range 1.0-2.75 Hz activity in session 2, while oxazepam decreased bodys way at 1.0 to 2.75 Hz and increased activity at 2.