DISTRIBUTION AND METABOLISM OF NOREPINEPHRINE AFTER ITS ADMINISTRATION INTO CEREBROVENTRICULAR SYSTEM OF CAT

Five μc of dl-3H-norepinephrine was injected into the cerebroventricular system of cat brain by means of stereotaxically implanted cannulae in the third or lateral ventricles. At various times after its administration various brain regions were examined for content of 3H-norepinephrine, 3H-normetanephrine, 3H-deaminated catechol metabolites and 3H-deaminated O-methylated metabolites. After the injection into the left lateral ventricle, 3H-norepinephrine was concentrated in the left caudate nucleus and hypothalamus. Lesser amounts were found in the left hippocampus, the wall of the left lateral ventricle, brain stem and cerebellum. After injection into the third ventricle, 3H-norepinephrine was retained primarily by areas caudal to the third ventricle (hypothalamus and brain stem). Thus, the regional distribution of 3H-norepinephrine depends upon the site of injection and the ability of various areas lining the ventricular system to accumulate norepinephrine. The major metabolite in each area was 3H-normetanephrine. Much smaller amounts of deaminated metabolites were detected. The pattern of metabolites was not affected by various anesthetic agents and remained relatively constant over a 24-hr period after injection of 3H-norepinephrine. Pretreatment with a monoamine oxidase inhibitor did not alter the brain content of endogenous or 3H-norepinephrine but did increase the percentage of 3H-normetanephrine. Pretreat- ment with reserpine reduced endogenous levels of norepinephrine and 3H-norepinephrine but increased the percentage of 3H-normetanephrine and 3H-deaminated metabolites in all brain regions. © 1969.