Expression of Syt1^{B-D3.4N.Scer\UAS} under the control of Scer\GAL4^elav.PLu largely suppresses the asynchronous component of release seen in Syt1^N13/Syt1^AD4 embryos when evoked release properties are recorded from muscle 6 following motor nerve stimulation in 4mM extracellular Ca[2+]. Only a small amount of residual synchronous release is seen in these embryos and the total charge transfer is dramatically reduced, similar to Syt1^N13/Syt1^AD4 embryos. Syt1^N13/Syt1^AD4 embryos expressing Syt1^{B-D3.4N.Scer\UAS} under the control of Scer\GAL4^elav.PLu show an enhanced rate of spontaneous release compared to controls.

Embryos expressing Syt1^{B-D3.4N.Scer\UAS} under the control of Scer\GAL4^elav.PLu in a Syt1^N13/Syt1^AD4 background show a similar level of hypertonic stimulated release as controls.

Following a 50 Hz, 10 s stimulus, the peak ΔF/F SpH change in Syt1^AD4/Syt1^N13; Syt1^{B-D3.4N.Scer\UAS} Scer\GAL4^elav.PLuflies is reduced compared to controls, which agrees with prior electrophysiological demonstration of a decrease in evoked release. A slowed endocytosis rate constant is found at Syt1^{B-D3.4N.Scer\UAS} rescue synapses, with an average endocytic value that is more than 2-fold slower than controls. Increasing the Ca[2+] concentration speeds the rate of endocytosis, although not to control levels.

Larvae expressing syt^{B-D3.4N.Scer\UAS} under the control of Scer\GAL4^elav.PLu in a syt^AD4 background show a reduced mean excitatory junction potential (EJP) amplitude at the neuromuscular junction compared to syt^AD4 mutant larvae. The Ca²⁺ dependence of neurotransmitter release in larvae expressing syt^{B-D3.4N.Scer\UAS} under the control of Scer\GAL4^elav.PLu in a syt^AD4 background is significantly shifted compared to the Ca²⁺ dependence of neurotransmitter release in larvae expressing syt^Scer\UAS.cMa under the control of Scer\GAL4^elav.PLu in a syt^AD4 background. Expression of syt^{B-D3.4N.Scer\UAS} under the control of Scer\GAL4^elav.PLu in an otherwise wild-type background reduces the mean EJP amplitude at the neuromuscular junction by 53% compared to wild type.