The mean amplitudes of spontaneous as well as evoked synaptic currents at the neuromuscular junction are smaller in apt^MY7919 larvae than in wild type. These effects are seen at 0.5mM and 0.3mM Ca²⁺ for both spontaneous and evoked synaptic currents, while at 0.2mM Ca²⁺ these effects are seen for spontaneous synaptic currents, but for evoked synaptic currents, no statistical difference between amplitudes in the mutant and wild type are recorded. Failure of stimulation of the nerve or ventral cord is higher in apt^MY7919 mutants than in wild type at any given external concentration of Ca²⁺. Additionally, the mean amplitude of miniature synaptic currents is smaller in apt^MY7919 mutants than in wild-type embryos. Finally, the unitary current amplitudes of junctional glutamate receptor channels are slightly but significantly smaller in apt^MY7919 mutants than in wild type.

Defects in synaptic transmission. The probability of transmitter release is lower and the amplitude of the junctional single channel current is slightly reduced.

Movements of homozygous embryos are quite sluggish and most do not hatch. Electrophysiological studies in the neuromuscular junction show that the probability of transmitter release is much lower than normal and the amplitude of junctional single channel current is slightly reduced.