Presence, distribution and pharmacology of conjugated catecholamines in the rat spinal cord

A method is described for the assay of conjugated catecholamines in the brain and spinal cord. Employing this method, the distribution of conjugated norepinephrine (NE) and dopamine (DA) was evaluated in the 5 main regions of the rat spinal cord and compared with those in the hypothalamus. In the spinal cord 26-35% of total catecholamines are conjugated. The percent of NE conjugated in the hypothalamus NE is about 17%, while that of DA is around 12%. Acute treatments with amphetamine, desmethylimipramine and haloperidol failed to change the concentrations of both total and conjugated NE and DA in the cervical spinal cord. Only amphetamine increased hypothalamic conjugated NE. It is concluded that evaluation of central conjugated catecholamines may provide an additional dimension to our ability to critically assess the mechanisms of action of drugs on central catecholamines.