EFFECT OF D-FENFLURAMINE ON HUMAN EXPERIMENTAL ANXIETY

To investigate the role of 5-HT in human anxiety, the 5-HT releaser an d uptake blocker d-fenfluramine (FEN) was administered to healthy volu nteers under two models of experimental anxiety The first was a simula ted public speaking (SPS) test consisting of talking in front of a vid eo camera. anxiety being evaluated mainly by self-rating scales. The s econd was a conditioned fear test, in which the changes in skin electr ical conductance caused by a tone associated once with an aversive whi te noise were measured. The doses of 15 and 30 mg FEN, PO, decreased a nxiety induced by SPS in a dose-dependent way, as indicated by the anx iety factor of Norris Visual Analogue Mood Scale. In the conditioned f ear test, however, the amplitude and level of skin conductance respons es to the conditioned aversive stimulus were not significantly changed by FEN. The differential effects of FEN in these human experimental m odels of anxiety, together with similar results reported in rats. supp ort the view that 5-HT exerts a dual action on brain mechanisms regula ting anxiety, facilitating conditioned while inhibiting unconditioned fear. The presumed reduction in unconditioned fear caused by FEN may h ave implications for the treatment of panic disorder.