Researchers in the Littleton group at MIT specifically study the effects of mutations on neurons in Drosophila. By name or number, identify all of the following three mutations that would cause a gluatamatergic neuron to lose the ability to engage in long-term potentiation, but not excitatory transmission. 1) Loss-of-function mutation in AMPA receptor 2) Constitutive binding of Mg^2+ to NMDA receptor 3) Loss of function mutation in the glutamate release pathway