At Metabotropic Receptors, A(n)

At metabotropic receptors, a(n)

A) neurotransmitter binding to a receptor stimulates a G- protein, which then activates a second messenger through one or more enzymatic actions.
B) neurotransmitter binding to a receptor opens channels that are a separate protein from the receptor.
C) neurotransmitter binding to a receptor opens or closes channels that are part of the same protein as the receptor.
D) ion binding to a receptor opens channels in the plasma membrane.
E) neurotransmitter binding to a receptor opens or closes channels that are a separate protein from the receptor.