Striatal dopamine and the interface between orienting and ingestive functions.

Recent lesion experiments have implicated forebrain catecholaminergic projections in a unique switching mechanism that enables sensory orientation to occur during ongoing feeding behavior. Unit recording studies indicate that there is a population of neurons in the striatum that respond to tactile stimulation only while an animal is eating. These sensory-related cells may serve as part of a system that diverts attention away from ingestive behavior. In the present study, 6-hydroxydopamine was infused directly into the striatum in rats to eliminate the dopaminergic input specifically to this region. The animals were tested for their reactions to tactile stimulation of the vibrissae during or in the absence of eating. During noneating trials, orienting was rapid and reliable to stimuli presented on either side of the body midline. While eating, contralateral orienting never occurred, even when the stimulation was intense, whereas ipsilateral orienting was unaffected. It was suggested that the capacity to disengage from ingestive behavior may depend importantly on the integrity of dopaminergic input to the striatum.