The effects of neomycin on membrane properties and discharge activity of an isolated sensory neuron

The effects of neomycin sulfate were examined upon the discharge activity and electrical membrane properties of an isolated invertebrate sensory neuron, the crayfish stretch receptor neuron. Neomycin depressed cell discharge activity in a concentration-dependent manner over the concentration range of 0.01-1.0 mM. Significant concentration-related increases were observed in the resting membrane potential and the width of the orthodromic action potential. There was a significant concentration-dependent decrease in the fast rising phase of the antidromic action potential. Significant changes also were observed in other electrical properties such as membrane resistance, but these were found not to be concentration related. The most significant change was membrane hyperpolarization, which could account for the depression of cell discharge activity. The observed changes are consistent with a neomycin-induced change in the membrane potassium conductance. It is proposed that the neural effect of neomycin is a selective interaction with the neuronal membrane phospholipids.