When a Neurotransmitter Molecule Binds Briefly with a Receptor Site

When a neurotransmitter molecule binds briefly with a receptor site, changes occur in the receiving neuron's membrane. If there is a voltage shift in a negative direction then the effect is:

A) inhibitory, and so the probability that the receiving neuron will fire decreases.
B) likely to lead to the development of multiple sclerosis.
C) excitatory, and so the probability that the receiving neuron will fire increases.
D) likely to lead to the development of Parkinson's disease.