SELECTIVE NEUROKININ NK1 AND NK2 RECEPTOR AGONISTS INFUSED IN THE SUBSTANTIA-NIGRA OF THE RAT INCREASE VACUOUS CHEWING

Bilateral intranigral infusion of selective neurokinin NK1 and NK2 rec eptor agonists were made in freely moving rats followed by measurement s of vacuous chewing frequencies for 30 min post-infusion. The NK1 rec eptor agonist, [Pro9] substance P, induced an immediate dose-related e levation of non-object directed vacuous chewing movements. There was a linear dose-response relation in the 0.5-5 nmol dose range. In experi ments with the NK2 receptor agonist, [Lys5,MeLeu9,Nle10]neurokinin A-( 4-10), the highest dose, 4.8 nmol, caused a less intensive but longer lasting increase of the vacuous chewing movement frequency. These find ings may imply a role for neurokinins in the regulation of oral moveme nts.