In vivo dialysis measurements of dopamine and DOPAC in rats trained to turn on a circular treadmill.

In vivo dialysis was used to measure extracellular fluid concentrations of dopamine and dihydroxyphenylacetic acid (DOPAC) in rats which were trained to run on a circular disk treadmill for water reinforcement. Turning resulted in bilateral increases in DOPAC in lateral striatum as well as nucleus accumbens/medial striatum. Dopamine release showed small but not significant increases at both sites. Changes in DOPAC release were not lateralized. Free drinking without circling also resulted in significant increases in DOPAC in these two brain areas. During free drinking, dopamine release was significantly increased in lateral striatum but not in nucleus/medial striatum. These experiments indicate that dopamine metabolism is increased in rat striatum and nucleus accumbens in animals running on circular treadmills as well as by free drinking.