Vol. 6, No. 1, 2000 Page 4

Fenfluramine `challenge' adds to evidence of
serotonin's role in aggression, impulsivity

The impulsive and aggressive behavior of male criminals with conduct disorder drops significantly when they are given a serotonin-enhancing drug, according to a new study by Don Cherek and Scott Lane. The researchers say their findings "are consistent wit th a large body of data linking reduced serotonin function and aggressive behavior and impulsivity."

The researchers evaluated the responses of 10 young male criminals diagnosed with conduct disorder to a challenge with d,l-fenfluramine, a drug that makes serotonin more available to brain cells. Participants repeatedly performed two different tests, the Point Subtraction Aggression Paradigm (PSAP) and an impulsivity test, while receiving a placebo or one of three different d,l-fenfluramine doses.

"d,l-fenfluramine produced a significant, dose-dependent decrease in aggressive responding in the PSAP sessions 2 to 4.5 hours after dosing," the researchers say. "All ten subjects decreased their aggressive responding following the highest 0.8 mg/kg dose e." Subjects with the highest rates of baseline aggression exhibited the largest decreases in aggression when taking the highest dose of d,l-fenfluramine. Responses were similar on the impulsivity test, with impulsive responses d decreasingly significantly in a dose-dependent manner.

Individuals taking the PSAP have three response options: an aggressive response, an "escape" response, and a response that is reinforced by money. During d,l-fenfluramine treatment, there were no decreases in the monetary response (which actually increase ed) or the escape response. This indicates, the researchers say, that the decrease in aggressive responding was not due merely to sedation, which would have influenced the rates of all responses.

Cherek and Lane caution that all of their subjects had a history of conduct disorder, and that results may be different in subjects without a history of conduct problems.


"Effects of d,l-fenfluramine on aggressive and impulsive responding in adult males with a history of conduct disorder," Don Cherek and Scott Lane, Psychopharmacology, Vol. 146, 1999, pp. 473-481. Address: D. R. Cherek, Department of Psychiatry and Behavioral Science, University of Texas-Houston Health Science Center, 1300 Moursund Street, Houston, TX 77030-3497.

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