SUMMARY The impedance of the epigastrium to a 4 mA, 100 KHz AC current increases while liquids of low electrical conductivity are being drunk. Logically, the decline which follows occurs as the liquid leaves the stomach. This impedance measurement of gastric emptying proved comparable with the dye dilution method. In a placebo controlled trial the impedance method recorded significantly faster gastric emptying rates after metoclopramide. The impedance trace contains regular activity in the 2-4 cycle/min range consistent with gastric contractions. This non-invasive and technically simple method may thus provide a measure of simultaneous gastric emptying rates and motility.

5AD1 Twelve healthy male volunteers participated in four experimental occasions during each of which they were dosed with one of the following anti-psychotic drugs: chlorpromazine (50 mg), haloperidol (3 mg), sulpiride (400 mg) and placebo. Drugs were allocated to subjects in a double-blind, crossover fashion. 2 The subject's mood state, psychometric performance and electroencephalogram (EEG) were assessed pre-dose, and at 2, 4, 6, 8, 24 and 48 h post-dose. Mood states were assessed using 16 visual analogue scales and psychomotor performance was measured using the following tests: elapsed time estimation, tapping rate, choice reaction times, a rapid information processing task, flash fusion threshold, a manipulative motor task, digit span, body sway and tremor. 3 Chlorpromazine and haloperidol significantly reduced subjective ratings of 'alertness' and 'contentedness', and haloperidol significantly reduced feelings of 'calmness'. Sulpiride did not significantly affect any of the visual analogue scales. 4 All three anti-psychotic drugs had similar EEG effects with peak effect 2 to 4 h postdose. The profile was characterised by an increase in the proportion of slow wave activity (delta and theta) as well as decreased alpha (8-14 Hz) and faster (beta) wave activity. 5 Chlorpromazine reduced tapping rate and increased choice reaction movement times. Haloperidol reduced the flash fusion threshold frequency at 6 h post-dose. Sulpiride prolonged the duration of the manipulative motor task, particularly at 48 h postdose.6 All three anti-psychotic drugs impaired performance on the rapid information processing task. Chlorpromazine significantly reduced the number of correct letter pair identifications at 2, 4 and 6 h post-dose, haloperidol at 4, 6, 8, 24 and 48 h post-dose, and sulpiride at 24 h post-dose. 7 It is concluded that the EEG and the rapid information processing task are sensitive methods for detecting the central effects of anti-psychotic drugs in normal volunteers.

The effects of practice on a range of performance measures often used in studies of psychoactive drugs have been assessed in 50 normal healthy adult volunteers, during 10 practice sessions over an 8-day period. There was no dramatic effect of practice on any of the parameters measured, only one of the mean values at the tenth session exceeded one standard deviation of the mean of the first session (manipulative motor task). Practice did not materially affect performance on elapsing time estimation, tapping rate, body sway measured by a ultrasonic method or rapid visual information processing task variables. There tended to be a non-significant, exponential learning curve for choice reaction response and movement times to visual stimuli, flash fusion threshold and the manipulative motor task, with a statistically significant practice effect on all 16 visual analogue scales used; a plateau was apparently achieved by the fifth practice session for all these parameters. There was a statistically significant straight-line improvement in digit span across the 10 sessions. It is concluded that for most simple measures of performance used in psychopharmacology including visual analogue scales, four pre-study training sessions are necessary, and that direct methods of recording body sway are preferred to indirect methods such as the balance platform.

The quantitative electroencephalogram (EEG) and plasma concentration of the antidepressant paroxetine were monitored in five normal volunteers after a single oral dose of 70 mg paroxetine and placebo. Peak plasma concentration occurred 4-6 h post-dose. Placebo had little effect on the EEG but the effects of paroxetine were statistically significant at 6 h post-dose. The EEG changes after treatment consisted of a decrease in delta and theta activity (less than 8 Hz) and increase in beta activity (greater than 12 Hz). These changes were still evident 72 h after treatment. The EEG profile obtained with 70 mg paroxetine is similar to that reported for other antidepressant 5-HT uptake inhibitors, but dissimilar to the classical, sedative antidepressants.

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