The concentration of norepinephrine in the hippocampus of rats anesthetized with halothane (Wyeth-Ayerst, Philadelphia, Pa) is found to be markedly increased, presumably due to the stress of handling and administering the anesthetic. This increased norepinephrine concentration persists for about 50 minutes but is obliterated when the anesthetized rat is concussed. This 50-minute period corresponds to the time it takes for a rat (or human), comatose for 1-2 seconds following concussion, to regain normal memory. No changes in 3,4-dihydroxybenzene-acetic acid (DOPAC), 3-(3,4-dihydroxyphenyl) alanine (L-DOPA), and 3,4-dihydroxybenzylamine (DHBA) were noted. 5-Hydroxy indole acetic acid (HIAA) showed a depression at 5 minutes and again at 30 minutes, changes that were consistent but not considered statistically significant.