Intranigral tachykinin NK3 receptor agonist elicits oral movements in rats

Synthetic agonists for the tachykinin NK1 and NK3 receptors were bilaterally infused at three dose levels (4.2, 0.17, and 0.007 nmol) into each substantia nigra of freely moving rats and oral behaviors were monitored for 30 min postinfusion. It was found that all doses of senktide, an agonist at the NK3 receptor, induced a significant increase of nonobject-directed chewing, vacuous chewing movements (VCM). The highest dose of senktide produced the greatest effect (p less than 0.001) and precipitated wet shakes for about 15 min after infusion. Septide, selective at the NK1 receptor, was without effect on oral behavior. The present results suggest that NK3 receptor-active peptides might be symptom inducers in oral dyskinesia.