Muscle fibers from Drosophila larvae show an L-glutamate-sensitive membrane potential. Bath-applied L-glutamate depolarizes the muscle in the range from 0.5 to 20/zM. Greater concentrations of the agonist repolarize the fibers. The repolarizing effect disappears if chloride is replaced by sulfate in the external medium. Intracellular recordings show the occurrence of depolarizing and hyperpolarizing spontaneous miniature postsynaptic potentials (smpp). Patch-clamp studies indicate the presence of two types of receptor channels: (i) an anion-selective channel activated by both L-glutamate and GABA. In outside out-patches, bathed in symmetrical 140 mM C1-and 200/zM GABA, the channel displays conductance substates of 40, 80 and 1 l0 pS. In the presence of 200/zM L-glutamate only the 40 and 80 pS substates are observed; (ii) a cation-selective channel activated only by L-glutamate that has a conductance of 104 pS in cell-attached patches (128 mM Na + outside). The presence of these two types of receptor channels in Drosophila muscle may explain the effect of bath-applied L-glutamate on membrane potential and the presence of inhibitory and excitatory smpp.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.