Cellular composition and circuit organization of the locus coeruleus of adult mice

The locus coeruleus (LC) houses the vast majority of noradrenergic neurons in the brain and regulates many fundamental functions, including fight and flight response, attention control, and sleep/wake cycles. While efferent projections of the LC have been extensively investigated, little is known about its local circuit organization. Here, we performed large-scale multipatch recordings of noradrenergic neurons in adult mouse LC to profile their morpho-electric properties while simultaneously examining their interactions. LC noradrenergic neurons are diverse and could be classified into two major morpho-electric types. While fast excitatory synaptic transmission among LC noradrenergic neurons was not observed in our preparation, these mature LC neurons connected via gap junction at a rate similar to their early developmental stage and comparable to other brain regions. Most electrical connections form between dendrites and are restricted to narrowly spaced pairs or small clusters of neurons of the same type. In addition, more than two electrically coupled cell pairs were often identified across a cohort of neurons from individual multicell recording sets that followed a chain-like organizational pattern. The assembly of LC noradrenergic neurons thus follows a spatial and cell-type-specific wiring principle that may be imposed by a unique chain-like rule.

Automated summary

This study conducted large-scale multipatch recordings of noradrenergic neurons in the locus coeruleus (LC) of adult mice to examine their morpho-electric properties and interactions. LC noradrenergic neurons were found to be diverse and could be classified into two major morpho-electric types. These neurons were connected via gap junction at a similar rate to their early developmental stage and other brain regions. Electrical connections primarily occurred between dendrites and were restricted to narrowly spaced pairs or small clusters of neurons of the same type. Additionally, chain-like organizational patterns of more than two electrically coupled cell pairs were often identified. The assembly of LC noradrenergic neurons follows a spatial and cell-type-specific wiring principle, possibly imposed by a unique chain-like rule.