In the other family, termed metabotropic receptors (eg, serotonin, alpha - and beta-adrenergic, and dopaminergic receptors), neurotransmitters interact with G proteins and activate another molecule (second messenger such as cAMP) that catalyzes a chain of events through protein phosphorylation, calcium mobilization, or both; cellular changes mediated by second messengers are slower and permit finer tuning of the rapid ionotropic neurotransmitter response.