Tolerance to the increase of striatal homovanillic acid elicited by several anorectic drugs.

Several anorectic drugs affect dopamine metabolism in the rat striatum, increasing the concentration of homovanillic acid (HVA). However 1- and d-amphetamine and mazindol develop a tolerance to the HVA increase. On the contrary, the effect of fenfluramine and S 992 is not reduced by sub-chronic treatments. Moreover, a cross-tolerance to this biochemical effect develops between amphetamine and mazindol, but pretreatment with fenfluramine or with S 992 does not induce cross-tolerance to amphetamine.