Relationships between central nervous system noradrenergic function and plasma and urinary concentrations of norepinephrine metabolites.

The available evidence suggests that there is an interaction or linkage between brain adrenergic systems and the functioning of peripheral CA neurons, particularly those in the sympathetic nervous system. Significant correlations between brain, CSF, plasma, and urinary concentrations of NE and MHPG have been observed by several different groups, and these are reviewed and summarized. While these correlations may occur in part because of a direct contribution of brain MHPG to peripheral pools of MHPG, it is also likely that the mechanism underlying these relationships resides in an interactive linkage between central and peripheral adrenergic systems. The use of plasma and urinary MHPG as a probe for central adrenergic function is discussed in relationship to these noted correlations and the central-peripheral interactive paradigm. The question of how well a peripheral adrenergic measure reflects CNS NE neuronal activity is discussed. Finally, it is noted that the existence of interactions between central CA systems and the sympathetic nervous system broadens research strategies, since it can no longer be assumed that measures of plasma or urinary NE, NM, or VMA do not reflect central events because the quantities of these substances entering the periphery from brain are quite small.