PT - JOURNAL ARTICLE AU - ZIGMOND, MICHAEL J. AU - WURTMAN, RICHARD J. TI - DAILY RHYTHM IN THE ACCUMULATION OF BRAIN CATECHOLAMINES SYNTHESIZED FROM CIRCULATING H<sup>3</sup>-TYROSINE DP - 1970 Apr 01 TA - Journal of Pharmacology and Experimental Therapeutics PG - 416--422 VI - 172 IP - 2 4099 - http://jpet.aspetjournals.org/content/172/2/416.short 4100 - http://jpet.aspetjournals.org/content/172/2/416.full SO - J Pharmacol Exp Ther1970 Apr 01; 172 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 &amp; Wilkins Co.