Size of vesicle pools, rates of mobilization, and recycling at neuromuscular synapses of a Drosophila mutant, shibire.
Two vesicle pools, readily releasable (RRP) and reserve (RP) pools, are present at Drosophila neuromuscular junctions. Using a temperature-sensitive mutant, shibire(ts), we studied pool sizes and vesicle mobilization rates. In shibire(ts), due to lack of endocytosis at nonpermissive temperatures, synaptic currents continuously declined during tetanic stimulation until they ceased as the result of vesicle depletion. By then, approximately 84,000 quanta were released. Vesicles were mobilized from RP at a rate 1/7-1/10 of RRP. Cytochalasin D inhibited mobilization of vesicles from RP, allowing us to estimate the size of RRP as 14%-19% of all vesicles. Vesicle recycling supports synaptic transmission during prolonged tetanic stimulation and the maximum recycling rate was 1000 vesicles/s.
Delgado
R
R
Centro de Estudios Cientificos, Arturo Prat 514, Valdivia, Chile.
Maureira
C
C
Oliva
C
C
Kidokoro
Y
Y
Labarca
P
P
D000818:Animals; D015638:Cytochalasin D / Q000494:pharmacology; D004330:Drosophila; D029721:Drosophila Proteins; D034281:Dynamins; D004558:Electric Stimulation; D004705:Endocytosis / Q000235:genetics / Q000502:physiology; D005456:Fluorescent Dyes; D020558:GTP Phosphohydrolases / Q000235:genetics*; D009154:Mutation; D009469:Neuromuscular Junction / Q000378:metabolism*; D011726:Pyridinium Compounds; D000644:Quaternary Ammonium Compounds; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology; D013572:Synaptic Vesicles / Q000187:drug effects / Q000378:metabolism*; D013696:Temperature
D029721:Drosophila Proteins; C073804:FM1 43; D005456:Fluorescent Dyes; D011726:Pyridinium Compounds; D000644:Quaternary Ammonium Compounds; D015638:Cytochalasin D; D020558:GTP Phosphohydrolases; D034281:Dynamins; C439628:shi protein, Drosophila