LACK OF LONG-TERM CHANGES IN COCAINE AND MONOAMINE CONCENTRATIONS IN RAT CNS FOLLOWING CHRONIC ADMINISTRATION OF COCAINE

In previous studies, we reported time-dependent and dose-dependent cha nges in the rat dopaminergic receptor system following chronic adminis tration of cocaine. The aim of the present investigation was to monito r the concentration of monoamines (using HPLC-ECD) and cocaine (using GC-PCI/MS) in rat CNS following a dose schedule of 5, 10, 15, 20 and 2 5 mg/kg, i.p., b.i.d. for 21 days. 12 h after the last cocaine injecti on, cortical and striatal concentrations of monoamines and their metab olites were not significantly different in saline vs cocaine treated a nimals. In addition, the cocaine concentration in the brain regions ex amined did not change with the different doses used. Accumulation of a metabolite of cocaine (ecgonine methyl ester) was the only alteration found. These results indicate that alterations in the dopaminergic re ceptor system following chronic cocaine administration are not due to changes in neurotransmitter concentration or accumulation of cocaine i n the brain.