The neurochemical basis for the behavioral effects of triadimefon

Administration of triadimefon (TDF) [1-(4-chlorophenoxy)-3,3-dimethyl-1-(1-H-1,2,4-triazol-1-yl)-2-butanone] in rodents incites heightened locomotor and stereotypy response, primarily through potentiation of dopaminergic activity. In the present study, 8 male Sprague-Dawley rats received repeated injections, on alternate days (100 mg/kg, 14 days) of TDF or corn oil. Enhanced locomotor and stereotypy behavioral patterns occurred in response to TDF injections, lasting until the 12th day of injection. Tolerance to this effect was evident by a lack of response to TDF injection by the 14th day. Similarly, a withdrawal period and challenge dose of TDF (5 days, 25 mg/kg) was ineffective in espousing locomotor or stereotypy behavioral changes. Cross sensitization to cocaine was also evident, since withdrawal and a challenge dose (8 days, 5 mg/kg) was also ineffective. Adaptative biochemical changes in dopaminergic function were examined after both acute (100 mg/kg) and repeated administration of TDF (100 mg/kg, 14 days) by examining [3H]dopamine (DA) uptake and DA release in both striatal (ST) and nucleus accumbens (NA) tissue. In corroboration with behavioral pattern indicating development of tolerance, there were significant changes in dopaminergic function. Repeated TDF exposure in vivo resulted in significant attenuation of ST and NA DA uptake in response to TDF (10(-4) to 10(-7) M) or cocaine (10(-5) to 10(-8) M) in vitro. Acute exposure to TDF in vivo also attenuated ST DA inhibitory effects of cocaine and TDF. Repetitive administration of TDF in vivo had no effect on in vitro TDF- or amphetamine-stimulated release of ST or NA DA. However, there was a significant reduction in amphetamine-stimulated DA release in animals after acute exposure to TDF in vivo. It was concluded from this study that the effects of chronic TDF exposure may primarily involve effects on DA uptake in the ST and NA.