Changes in muscle action potentials of patients with diseases of motor units following the infusion of a peptide fragment of ACTH.
The polypeptides ACTH and ATCH4-10 (OI 63) witha sequence of amino acids H-Met-Glu-His-Phe-Arg-Trp-Gly-OH, have similar stimulating effects on motor units in lower mammals. Their actions differ primarily in that ACTH4-10 is not corticotropic. Since the corticotropic action of ACTH frequently presents a problem during its clinical use in treatment of motor unit diseases, the action of ACTH4-10 was studied in two patients with muscular atrophy. Prior to administration of ACTH4-10, stimulation of M. oppenens pollicis through the median nerve evoked muscle action potentials in both patients which progressively declined in amplitude. This decline was not observed subsequent to the infuscion of ACTH4-10 (3, 6 and 15 mg). The effect lasted partially in excess of at least 2 h. It is suggested that ACTH4-10 produces this effect by direct action on a peripheral component of the motor unit and/or indirectly by an action on the central nervous system.