Different alleles of para block synaptic transmission at different temperatures. Embryos raised at these restrictive temperatures show a dramatic reduction in GluR expression at the NMJ at the end of embryogenesis. Evidence is also provided that presynaptic electrical activity is required to localize GluRs to the synaptic site during synaptogenesis. Synaptic morphogenesis is independent of synaptic activity during embryogenesis, and it is concluded that postsynaptic activity, mediated through GluRs, similarly plays no role in synaptic morphogenesis in the embryo. Unlike synaptic structure, the size of the synaptic zone is significantly altered in line with alterations in presynaptic electrical activity.
Hyperactive synapses expand to occupy a large area of the muscle surface relative to wild type.
Likewise, inactive synapses occupy an even smaller synaptic domain relative to hyperactive synapses, although inactive synapses are not significantly smaller than wild type. Thus, activity modulates the size of the synaptic domain during synaptogenesis. Glutamate receptor channels in Drosophila embryos and larvae were examined with the patch-clamp technique in various configurations. In the cell-attached mode, only one type of channel is observed in the extrajunctional region at any stage. The burst duration histogram was fit with three exponentials.