Possible interactions between neomycin and calcium channels in abdominal skeletal muscle

The present study was performed to investigate whether neomycin, an aminoglycoside, interacts with calcium channels in the frog rectus abdominis muscle. We thus examined the effects of methoxyverapamil (D600), a dihydropyridine-sensitive calcium channel antagonist, and neomycin on contractions induced by acetylcholine (ACh; 10-6, 3 × 10 -6, 5 × 10-6, 10-5 and 5 × 10 -5 M), electrical field stimulation (EFS; 5, 8, 10 Hz, 15 V, 1 ms) and potassium chloride (KCl; 40 mM) in isolated frog rectus abdominis muscle. D600 (10-6 - 3 × 10-4 M) exhibited a concentration dependent inhibitory action on contractions evoked by ACh, EFS and KCl. Neomycin (10-5-5 × 10-4 M) significantly inhibited the contractions elicited by ACh and EFS in a concentration dependent manner but it failed to reduce the KCl-evoked contractions. These results suggest that the inhibitory action of D600 on ACh-, EFS- and KCl-induced contractions reflect the action of this agent on Ca2+-channel activity in the isolated frog rectus abdominis muscle. A similar mechanism may also be involved in the action of neomycin on the frog abdominal skeletal muscle