RESUMO
The effect of aminoglycoside antibiotics upon the electrically induced release of endogenous opioid peptides from the guinea-pig ileum was studied in vitro. Stimulation of guinea pig ileum at 10 Hz in normal Tyrode solution resulted in the naloxone sensitive depression of the twitch contractions of this muscle. Addition of aminoglycosides during 10 Hz stimulation diminished this naloxone sensitive depression in a dose dependent manner. IC50s of this effect of streptomycin, neomycin, kanamycin and gentamicin were found to be 2.54, 2.29, 1.36 and 0.7 mg/ml respectively. A 3.5 fold increase in the calcium concentration of media during 10 Hz stimulation significantly reversed the effect of aminoglycosides. It is concluded that aminoglycoside antibiotics exert their effect by interfering with trans-membrane movements of calcium at the nerve endings which is required for the electrically induced release of opioid peptides.