Effect of propanolol on monosynaptic reflex activity during a task.
20 normal healthy subjects in a double-blind crossover experiment were given a table of either 40 mg propranolol or placebo half an hour before the beginning of the experiment. At rest and during the performance of a task, hert rate, Achilles tendon (T) and Hoffmann (H) reflexes were recorded. No increase in heart rate occurred during the task in the propranolol session. The increase of T-reflex amplitude, a common finding during the task under consideration, was larger in the propranolol session. No difference with H reflexes was found. It is concluded that the increase of T-reflex amplitudes during the task is caused only by fusimotor and not by sympathetic activity. It is speculated that if the sympathetic system plays a role at all, the effect on the T reflex is depressive rather than facilitating.
D000293:Adolescent; D000328:Adult; D002986:Clinical Trials as Topic; D004311:Double-Blind Method; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D008297:Male; D009047:Motor Neurons, Gamma / Q000187:drug effects; D011433:Propranolol / Q000494:pharmacology*; D012023:Reflex, Monosynaptic / Q000187:drug effects*; D012026:Reflex, Stretch / Q000187:drug effects; D013564:Sympathetic Nervous System / Q000187:drug effects; D013647:Task Performance and Analysis
D011433:Propranolol