Effects of locally applied dopamine to the nucleus accumbens on the motor activity of normal rats and following ?-methyltyrosine or Reserpine

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Abstract
The motor activity of rats was investigated following bilateral application of various doses (0–80 μg) of dopamine to the nucleus accumbens. A high dose (80 μg) of dopamine increased the motor activity of normal as well as α-methyltyrosine- and reserpine-treated rats. It also increased the late motor activity (6–9 min) of normal rats, probably due to stimulation of postsynaptic dopamine receptors. Lower doses (10–40 μg) of dopamine suppressed initial (0–3 min) motor activity of normal rats, perhaps due to stimulation of dopamine autoreceptors on the dopamine nerve terminals in the nucleus accumbens with a subsequent inhibition of dopamine neurotransmission. An intermediate dose (40 μg) of dopamine was able to restore the motor activity of α-methyltyrosine-treated but not of reserpine-treated rats at all time intervals. This difference, indicating a restoration of the normal pattern of habituation by dopamine only in animals pretreated with α-methyltyrosine, suggests that normal behaviour is dependent on release of dopamine by nerve impulses.