Neurochemical basis for cocaine and methamphetamine interactions

We have evaluated the responses of rat monoaminergic pathways to combinations of cocaine and methamphetamine (METH) administrations and found that these two commonly abused stimulants significantly interact. A 7-day pretreatment with daily doses of cocaine enhanced the neurochemical changes induced by multiple doses of METH in the dopaminergic and serotonergic systems of the basal ganglia and frontal cortex. When cocaine was administered concurrently, it attenuated or blocked the serotonergic changes caused by multiple doses of METH, but it did not interfere with the METH-mediated changes in the dopaminergic system.