7. You stimulate a presynaptic cell and record from the postsynaptic neuron of each pair. For each mutation below, describe the following: i) After the first stimulus, how does the excitatory postsynaptic potential (EPSP) you record from the postsynaptic neuron differ from the EPSP recorded from a wild-type animal? Does it increase, decrease, stay comparatively the same, or fail to be generated at all?

ii) After five stimulations of the presynaptic cell in quick succession, how does the EPSP you record from the mutant animal differ from that in the same experiment on a wild-type animal?
Explain your reasoning in each case.

The mutations are as follows:
7A. Mutation of the voltage-gated Ca2+ channels of the presynaptic terminal. The mutant channels have a lower opening threshold.

7B. Mutation of the Ca2+ binding sites of synaptotagmin. The mutant protein does not bind Ca2+.