Depression of synaptic efficacy in high- and low-output Drosophila neuromuscular junctions by the molting hormone (20-HE).
The molt-related steroid hormone, 20-hydroxyecdysone (20-HE), was applied to muscles 6 and 7 of third instar larval of Drosophila melanogaster neuromuscular junction preparations to examine if rapid, nongenomic responses could be observed as was shown recently to occur in crustacean neuromuscular junctions. At a dose of 10 microM, the excitatory junction potentials were reduced in amplitude within minutes. To elucidate the site of action of the hormone, focal-macropatch recordings of synaptic currents were obtained over the neuromuscular junctions. The results showed that the high-output (Is) and the low-output (Ib) motor nerve terminals, which innervate muscles 6 and 7, released fewer synaptic vesicles for each stimulation while exposed to 20-HE. Because the size and shape of synaptic currents from spontaneous releases did not change, the effects of the 20-HE are presynaptic. The rapid effects of this hormone may account in part for the quiescent behavior associated with molts among insects and crustaceans.
Thomas Hunt Morgan School of Biological Sciences, Nerve-Muscle Group, University of Kentucky, Lexington, Kentucky 40506-0225, USA.
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Ruffner
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Cromarty
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Cooper
D000818:Animals; D004331:Drosophila melanogaster; D004441:Ecdysterone / Q000494:pharmacology*; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects; D066298:In Vitro Techniques; D007814:Larva / Q000502:physiology; D009046:Motor Neurons / Q000187:drug effects / Q000502:physiology; D009132:Muscles / Q000294:innervation; D009469:Neuromuscular Junction / Q000187:drug effects* / Q000502:physiology; D018408:Patch-Clamp Techniques; D009435:Synaptic Transmission / Q000187:drug effects* / Q000502:physiology; D013572:Synaptic Vesicles / Q000187:drug effects; D013997:Time Factors
D004441:Ecdysterone