Spontaneous release of multiquantal miniature excitatory junction potentials induced by a Drosophila mutant.

Abstract

1. Intracellular recordings were made from muscle fibre No. 6 of the dorsal longitudinal flight muscle (DLM) of Drosophila melanogaster in both wild‐type flies and the temperature‐sensitive paralytic mutant, shibirets‐1 (shi). 2. Continuous recordings of the miniature excitatory junction potentials (MEJPs) in this fibre were made as the temperature was changed from 19 to 29 degrees C, and back to 19 degrees C. In shi flies, synapses become depleted of vesicles at 29 degrees C due to a temperature‐dependent blockage in the recycling process, while transmitter release proceeds normally. When the temperature is lowered to 19 degrees C, recycling is allowed to proceed and recovery of the full complement of synaptic vesicles gradually occurs in about 20 min. 3. It was observed that the MEJP amplitude distribution in shi flies was unimodal at 19 degrees C prior to heating (as was wild‐type), but during recovery from 8 min exposure to 29 degrees C became multimodal, with peaks at roughly integral multiples of the original peak prior to heating. This effect was never seen in wild‐type flies. 4. Also, during recovery, the MEJP did not occur randomly, but rather occurred in a clustered fashion. 5. It is concluded that during recovery from depletion in shi neuromuscular junctions, a condition exists which causes the synchronization of spontaneous release, causing multiquantal MEJPs or clustering of MEJPs, depending on the degree of synchronization. 6. The possible role of Ca2+ in this phenomenon is discussed.

Release and Recycling of the Readily Releasable Vesicle Population in a Synapse Possessing No Reserve Population

“…In MEJP amplitude distribution of the previously depleted synapses (dashed line), note the peaks at multiples of the original peak of 0.5 mV, suggesting the presence of multiquantal MEJPs. response decreased, the MEJP frequency also decreased, which was previously observed for the DLM as well (Ikeda and Koenig 1988). During the initial recovery period, spontaneous multiquantal release and clustered release similar to that observed in the DLM were observed as shown in Fig.…”

DrosophilaCAKI/CMG Protein, a Homolog of Human CASK, Is Essential for Regulation of Neurotransmitter Vesicle Release

“…The flies were then submerged with adult fly physiological saline (Kawasaki et al 1998). A piece of polyethylene tubing (1.0 mm ID, 1.5 mm OD, Clay Adams) connected to a hole in the bottom of the slab, continuously delivered fresh air to fly thorax spiracles, maintaining a constant physiological oxygen afflux to indirect flight muscle (IFM) fibers (Ikeda and Koenig 1988). Experiments were carried out at room temperature (22°C).…”

“…In this experimental protocol, however, the temperature of the extracellular saline was maintained at 19°C by means of a Peltier device. This temperature was chosen in view of the high frequency of MEPPs registered in IFM fibers at room temperature: the lower temperature was previously shown to reduce the MEPPs frequency, permitting a clearer discrimination of the single events (Ikeda and Koenig 1988). After allowing the flies to recover from anesthesia for 15 min, an intracellular glass recording microelectrode (1.2 mm OD, 0.9 mm ID, tip diameter: 0.5 m, Hingelborg) was inserted into IFM fibers through a hole made in the scutellum.…”

Loss of Flight and Associated Neuronal Rhythmicity in Inositol 1,4,5-Trisphosphate Receptor Mutants ofDrosophila

“…These phenotypes could also arise as a consequence of general defects in motor coordination. Therefore, we tested the motor response of itpr mutants in tests that measure climbing rate (Bainton et al, 2000), the jump response (Ikeda and Koenig, 1988a), and the cleaning reflex (Vandervorst and Ghysen, 1980;Burg and Wu, 1986). In all cases, the responses obtained were indistinguishable from wild type (data not shown).…”