Background: Knowledge of molecular marker (typically protein or mRNA)
expression in neural systems can provide insight to the chemical blueprint of signal processing
and transmission, assist in tracking developmental or pathological progressions,
and yield key information regarding potential medicinal targets. These markers are particularly
relevant in the mammalian brain in the light of its unsurpassed cellular diversity.
Accordingly, molecular expression profiling is rapidly becoming a major approach to
classify neuron types. Despite a profusion of research, however, the biological functions
of molecular markers commonly used to distinguish neuron types remain incompletely
understood. Furthermore, most molecular markers of mammalian neuron types are also
present in other organs, therefore complicating considerations of their potential pharmacological
Objective: Here, we survey 15 prominent neurochemical markers from five categories,
namely membrane transporters, calcium-binding proteins, neuropeptides, receptors, and
extracellular matrix proteins, explaining their relation and relevance to synaptic communication.
Method: For each marker, we summarize fundamental structural features, cellular functionality,
distributions within and outside the brain, as well as known drug effectors and
mechanisms of action.
Conclusion: This essential primer thus links together the cellular complexity of the brain,
the chemical properties of key molecular players in neurotransmission, and possible biomedical