VGlut¹/Df(2L)VGlut² mutant synapses exhibit a reduction in mEJP frequency without a reduction in mEJP amplitude. The distribution of mEJP amplitudes is not significantly different between wild-type and VGlut¹/Df(2L)VGlut² mutant synapses. These mutants exhibit a normal quantal size. There is no increase in post-synaptic response to glutamate in VGlut¹/Df(2L)VGlut² mutants compared to controls, indicating that the normal quantal size found in these mutants cannot be due to an increase in postsynaptic sensitivity to transmitter.

VGlut¹ homozygotes release fewer than half as many detectable quanta as wild-type larvae, while a further reduction of VGlut levels in VGlut¹/Df(2L)VGlut² mutants decrease the quantal frequency to about one-quarter of normal.

VGlut¹/Df(2L)VGlut² mutant synapses exhibit wild-type levels of vesicles. Within the first 100nm of the active zone, VGlut¹/Df(2L)VGlut² mutants exhibit only a 14% reduction in vesicle number. Even at 300nm from the active zone, the reduction is less than 20% in the mutant. However, this small decrease in the number of vesicles close to release sites is unlikely to account for the 4-fold reduction in mEJP frequency. The average active zone length, percent of bouton circumference occupied by active zones, and number of T-bars per active zone are unchanged in these mutants compared to controls.

Synaptic vesicles are smaller in VGlut¹/Df(2L)VGlut² mutants compared to controls by approximately 32%.

Vesicles are released at a similar rate to controls in VGlut¹/Df(2L)VGlut² mutants.