G-protein coupled receptors are targets for several psychiatric medications. Given what we know about these receptors, what is the ultimate result we will see when one of them is activated in a way that would potentiate an action?

Neurotransmission is unidirectional insofar as chemical and electrical conduction is concerned within the individual neuron. Of the following descriptions, which best characterizes the order of neurotransmitter/receptor interaction that results in an electrical signal impulse and the release of another neurotransmitter for interaction in the synaptic cleft (signal conduction through a neuron)?