RT Journal Article SR Electronic T1 DAILY RHYTHM IN THE ACCUMULATION OF BRAIN CATECHOLAMINES SYNTHESIZED FROM CIRCULATING H3-TYROSINE JF Journal of Pharmacology and Experimental Therapeutics JO J Pharmacol Exp Ther FD American Society for Pharmacology and Experimental Therapeutics SP 416 OP 422 VO 172 IS 2 A1 MICHAEL J. ZIGMOND A1 RICHARD J. WURTMAN YR 1970 UL http://jpet.aspetjournals.org/content/172/2/416.abstract AB The accumulation of H-catecholamines in brain was measured in rats given i. p. H3-tyrosine (H3-TYR). In animals injected at the same time of day, brain H3-TYR reached a peak within 10 minutes of injection and remained at this level for at least 120 minutes. Brain H3-catecholamine content was highest 60 minutes after injection. However, H3-catecholamine content corrected for the specific activity of H3-TYR during the accumulation period attained its peak within 10 minutes of the injection and remained at this level for the next two hours; this suggests that the newly synthesized catecholamine equilibrates rapidly with one of several brain pools. Animals maintained under light for 12 hr/day received H3-TYR at the middle or end of the daily light or dark period and were killed after 3 or 60 minutes. The accumulation of H3-catecholamine was significantly higher in the middle of the light period than in the dark period when correction was made for fluctuations in the specific activity of tyrosine. © 1970, by The Williams & Wilkins Co.