Systemic administration of amphetamine (1.25 mg/kg) produced increases of locomotion (including horizontal motion, vertical motion, and total distance travelled), elevations of turnings (including both clockwise and anticlockwise) and inhibition of postural freezing in freely moving rats. All the afore-mentioned activity measures induced by amphetamine were suppressed following electrolytic lesions of the paramedian reticular nucleus (PRN) in rat medulla. In addition, the spontaneous level of either the locomotor activity, the direction of turnings, or the postural freezing were slightly but significantly affected by the PRN lesions. In vivo voltammetric data revealed that amphetamine administration greatly enhanced the striatal dopamine release. Furthermore, the enhanced dopamine release in corpus striatum produced by amphetamine were greatly attenuated by PRN lesions. The results indicate that there exists a PRN-striatal dopamine link in rat brain which mediates the amphetamine-induced increases of locomotion and turnings, as well as decreases of postural freezing.
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