MSH/ACTH4-10 and task-induced increase in tendon reflexes and heart rate.

Earlier studies revealed that during a binary choice reaction task an increase of tendon reflex amplitudes and heart rate can be found, together with a suppression of heart rate variability. The results were interpreted as a task-induced increase in generalized arousal. In this study two experiments, consisting of a rest period and a binary choice reaction task, were done. In Experiment 1, twenty subjects, in a cross-over design, received 15 mg MSH/ACTH4-10 or a placebo. Only reflexes were recorded. In experiment 2, three groups of 9 subjects received either 30 or 15 mg MSH/ACTH4-10 or a placebo. Reflexes, heart rate and heart rate variability were recorded. Rest-task differences of reflexes and heart rate were enhanced by the drug. We hypothesized that MSH/ACTH4-10 intensified the arousal effect of the task.