Correlational analysis of central noradrenergic neuronal activity and sympathetic tone in behaving cats.

The activity of the noradrenergic (NA) neurons of the feline locus coeruleus complex (LCx) were correlated with changes in peripheral sympathetic tone in behaving cats. LCx NA neurons exhibit stereotypical changes in discharge rate across behavioral states, falling virtually silent during paradoxical sleep (PS). Simultaneous recordings from LCx NA neurons and the cervical sympathetic trunk demonstrated a tonic reduction in nerve activity during PS as well. LCx NA neurons were also found to fall silent during induction of the scruff immobility reflex and significant pupillary miosis was seen during this behavior as well. These data support the hypothesis that NA neurons in the brain are a central analogue of the peripheral sympathetic system and demonstrate that the two systems operate in an integrated fashion in the behaving cat.