A comparison of the fenfluramine-induced serotonergic syndrome in rats subacutely treated with either saline or D-amphetamine.

The purpose of this study was to assess the activity of the serotonergic transmitter system in vivo in rats previously exposed to repeated injections of either saline or d-amphetamine. To do so, components of the serotonin syndrome, as induced by various doses of fenfluramine, were scored both before and after a 15-day subacute regimen with these agents. Fenfluramine caused hindlimb abduction, forepaw padding, and straub tail behaviors to be expressed in both groups of animals within 30 min after dosing; little or no activity with respect to these behaviors was seen in either regimen during the 30-60 or 60-90 min intervals. However, body-shaking behavior was consistently observed in both treatment groups during each observation period. No differences in the serotonergic syndrome as a whole or in the expression of each individual component of the syndrome (i.e., hindlimb abduction, straub-tail, forepaw padding, body shakes) were noted either between or within regimens before or after subacute saline or d-amphetamine treatment. Thus, the previously observed decrement in fenfluramine's food intake suppressant action, which resulted from subacute d-amphetamine treatment, is not likely to be due to gross alterations in the central serotonergic system.