STUDY OF MUSCULAR EFFECTS OF SHORT-TERM PYRIDOSTIGMINE TREATMENT IN RESTING AND EXERCISING RATS

1. Pyridostigmine (PYR) pretreatment is used by the military to obtain 20-30% whole blood acetylcholinesterase (AChE) inhibition in order to enhance the effectiveness of the standard therapeutic regimen for poi soning by an organophosphate anticholinesterase agent. The present stu dy was undertaken to investigate in a rat model the potential muscle d amage produced by this pretreatment when given alone or combined with physical exercise. 2. Grip strength and biochemical measurements, i.e. serum creatine phosphokinase (CPK) activity and creatine urinary excr etion rate, together with histological studies, were performed in rest ing animals during a period of 14 days of PYR administration in a dose producing 20-30% whole blood acetylcholinesterase inhibition. No evid ence was found of a deleterious effect of this treatment on the skelet al muscle. 3. In contrast, following physical exercise, the same treat ment significantly exacerbated the biochemical changes reflecting a lo ss of integrity in skeletal muscles, namely, increased CPK and urinary creatine excretion rate. The significance of this observation remains to be clarified.