PHARMACOLOGICAL CHARACTERIZATION OF GROOMING INDUCED BY A SELECTIVE NK-1 TACHYKININ RECEPTOR AGONIST

Bilateral intranigral administration of the selective NK-1 tachykinin receptor agonist [AcArg(6),Sar(9),Met(O-2)(11)]SP6-11 (0-1 nmol total bilateral dose) selectively induced grooming in rats. This response wa s blocked by concurrent intranigral administration of the NK-1 tachyki nin receptor antagonist RP 67580 (2 nmol), but not by NK-2 (L-659,877) or NK-3 ([Trp(7), beta-Ala(8)]NKA(4-10)) antagonists. Pretreatment wi th systemic opioid (naloxone 1.5 mg/kg) and D-1 dopamine (SCH 23390 10 0 mu g/kg) receptor antagonists also attenuated tachykinin-induced gro oming, which was unaffected by D-2 dopamine (sulpiride 30 mg/kg) or 5- HT2A+C (ritanserin 2 mg/kg) antagonists. Grooming induced by intranigr al [AcArg(6),Sar(9),Met(O-2)(11)]SP6-11 was also attenuated by bilater al 6-hydroxydopamine lesions of the substantia nigra. These findings i ndicate that grooming induced by intranigral tachykinins reflects acti vation of NK-1 receptors and is dependent upon endogenous dopamine and consequent selective stimulation of D-1 dopamine receptors.