CHROMODACRYORRHEA AND REPETITIVE HIND PAW TAPPING - MODELS OF PERIPHERAL AND CENTRAL TACHYKININ NK1 RECEPTOR ACTIVATION IN GERBILS

The in vivo pharmacological profiles of the selective tachykinin NK1 receptor agonists, [Sar(9),Met(O-2)(11)]substance P and GR 73632, were examined in gerbils. Both agonists induced a pronounced chromodacryorrhea following intravenous injection which was stereoselectively antagonised by the tachykinin NK1 receptor antagonist, CP-99,994, but not by its inactive enantiomer, CP-100,263, or the rat-selective tachykinin NK1 receptor antagonist, RP 67,580. In contrast, chromodacryorrhea was not observed following intravenous injection of the selective tachykinin NK2 receptor agonist, [beta-Ala(8)]neurokinin A-(4-10), or the selective tachykinin NK3 receptor agonist, senktide. These results suggest that [Sar(9),Met(O-2)(11)]substance P-induced chromodacryorrhea results from activation of peripheral tachykinin NK1 receptors. Repetitive hind paw tapping was also observed in gerbils but only following intracerebroventricular injection of [Sar(9),Met(O-2)(11)]substance P or GR 73632. Furthermore, GR 73632-induced hind paw tapping was significantly attenuated by co-administration of the peptide tachykinin NK1 receptor antagonist, GR 82334, or intravenous injection of CP-99,994. Thus, in contrast to chromodacryorrhea, repetitive hind paw tapping may result from activation of central tachykinin NK1 receptors.