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.
Ruffner
M E
ME
Thomas Hunt Morgan School of Biological Sciences, Nerve-Muscle Group, University of Kentucky, Lexington, Kentucky 40506-0225, USA.
Cromarty
S I
SI
Cooper
R L
RL
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