Psychiatry Rrsrarch. 13, 31-43 Elsevier 31 Singeing Behavior and Plasma Amino Acids: A Possible Involvement of Brain Serotonin in Bulimia Nervosa Walter H. Kaye, Harry E. Gwirtsman. Timothy D. Brewerton, . David T. George, and Richard J. Wurtman Received March 24, 1987: revised version received July 20, /987; accepted July 30. /987. Abstract. It has been suggested that bingcing and vomiting behavior may be an attempt to supp re ss hunger or reduce dysphoria. Theoretically, such relationships could involve a mechanism whereby bingeing and vomiting<:hange plasma amino acicls which , in turn, enhance brain serotonin-mediated satiety and/or improvement in mood . This hypothesis is based on data showing that the intake of dietary carbohydrates increases the uptake of tryptophan (TRP), the of serotonin, into the brain by increasing the plasma TRP ratio (the ratio of the pl asma TRP concentration to the summed concentrations of other amino acids that compete with TRP for brain uptake). Plasma prolactin (PRL) release might renect the activation of this system . We found that an increase in the TRP ratio during bingei ng and vomiting was associat ed with satiety (i .e., cessation of bit •gei ng and vomiting}, but not change in mood. hi other words, bulimic subjects who de ve loped an increased plasma TRP ratio during bingeing and vomiting had fewer cycles of bingeing and vomiting and a greater increase in plasma PR L than did subjects who did not de velop an increase in th e plasma TRP ratio. This study rai ses the possibility that an incre ase in the TR P ratio may be associated with the termination of bingeing and vomiting, perhaps due to its effects . on brain serotonin metabolism. Key Words. Bulimia, bulimia nc:rvosa, serotonin, tryptophan, satiety, large neutral amino acids. I The distinguishing characteristics of the disorder bulimia-binge eating, the rapid consumption of a large quantity of food in a discrete period of time, usually< 2 hours (DSM- /11-R, American Psychiatric As sociation, 1987), invariably followed by purging- are poorly understood. These behaviors could simply be an attempt to satisfy hunger without gaining weight (Chiodo and Latimer, 1983). Alternatively, they ·may represent an attempt to use food to relieve dysphoria and/or anxiety (Abraham and Beaumont, 19 82; Johnson and Larson, 1982 ; Strober, 1984; Kaye et Walter H. Kaye, -- M.D .; is Program Director, Inpatient Eating Disorders Progra m, Department of Psychiatry. Univer sity of Pittsburgh, Pitt sburgh , PA. Harry E. Gwi rt sman. M.D ., is Assistant Professor of Psych ia try and Director. Unit 2 South , Department of _ Ps ychiat ry and Behavioral Sciences, Neuropsyc hi atric In stitute , Uni versity of Californ ia Los Angeles; Timothy D. Brewerton, M.D., is Med ical Staff Fell ow, La boratory of Clin ic al Science, Bi o medi cal Ps yc hiatry, Nati onal Institute of Mental He alth . Re th es d a. MD. David T. George. M.D ., is Senior Staff Fello"·· National Institute of Alc o hol Abu se and Alcohol ism , Bethesda, MD. Richard J. Wurtm a n, M.D., is Professor of Neuroendocrine Regulatio n. Ma ssac hu setts In stitute of Technology, Cambridge, MA. (Reprint rcquesu to Dr. W.H. Ka ye, WPIC, 3811 O'Hara St., Rm. 10 86, Pittsburgh, PA 15213, USA.) 0165-1781/ 88/ S03 .50 C> 19H8 El sevier Scientific Publishers Ireland Ltd. -; . -. -· .i!.._·_ : --. ,· ··· '-' -; ··:- .. . ·- :--·_: . --.: - -. ·.·:J·' ·- !i • "; . · . .. _ :-_. . ,, f . ... -- - _. _ ... _ .. -: .. _ . :' . . -- -·: - -