A medullary source of norepinephrine in cat cochlear nuclear complex.

Norepinephrine is believed to modulate important functions of the cochlear nuclear complex (CNC) such as the detection of signals in noise and the processing of timing cues. To better understand the impact of the noradrenergic system in the CNC, we used neurotransmitter immunohistochemistry combined with retrograde tract-tracing to identify the noradrenergic cell groups that project to the CNC. Here we present data showing that the CNC receives noradrenergic inputs from the A1 cell group located in the ventrolateral medulla. The projection from A1 to the CNC may be part of a system-wide modulation by the noradrenergic system based on stress and arousal level, or it may be part of a separate circuit that modulates its targets during survival behaviors.