Heterogeneity of mesencephalic dopaminergic neurons: From molecular classifications, electrophysiological properties to functional connectivity

The mesencephalic dopamine (DA) system is composed of neuronal subtypes that are molecularly and functionally distinct, are responsible for specific behaviors, and are closely associated with numerous brain disorders. Existing research has made significant advances in identifying the heterogeneity of mesencephalic DA neurons, which is necessary for understanding their diverse physiological functions and disease susceptibility. Moreover, there is a conflict regarding the electrophysiological properties of the distinct subsets of midbrain DA neurons. This review aimed to elucidate recent developments in the heterogeneity of midbrain DA neurons, including subpopulation categorization, electrophysiological characteristics, and functional connectivity to provide new strategies for accurately identifying distinct subtypes of midbrain DA neurons and investigating the underlying mechanisms of these neurons in various diseases. This review provides an in‐depth analysis of recent advancements in understanding the heterogeneity of midbrain dopamine (DA) neurons, encompassing the classification of subgroups, investigation of their electrophysiological characteristics, and exploration of their functional connectivity. The primary objective is to propose novel methodologies for accurately identifying specific subtypes of midbrain DA neurons and to investigate the underlying function of these neurons.