Interneuron Pharmaceuticals Inc. quickly sought to diffuse the impact of an animal study critical of the company's anti-obesity drug dexfenfluramine that was published last week by researchers at Johns Hopkins University and the National Institute on Drug Abuse.

Dexfenfluramine is believed to act on nerve cells containing the messenger serotonin, by mimicking the serotonin signal of satiety that is usually triggered by the intake of fats and carbohydrates. In their report in the Journal of Pharmacology and Experimental Therapeutics, the scientists reported that the loss of serotonin-bearing nerves in three monkeys was apparent as long as a year and a half after a high dose (5 mg/kg) of the drug given twice