Following behavior of resident mice after the introduction of the intruder into the home cage. The resident-intruder assay is taken as an index of negative phencyclidine (PCP)-induced behaviors. Adult male DBA/2 mice were housed in groups of five (intruder mice) or alone (resident mice) for 7–14 days. After an intruder was introduced into the home cage of a resident mouse, the saline treated resident mouse (n = 18) followed the intruder 3 times on average over the next 10 minutes. In contrast, the mice treated with 6 mg/kg (i.p.) followed the intruder significantly less (p. < 0.01, n = 42). ZJ43 (150mg/kg, i.p., n = 43) reversed the effects of PCP in this assay while the effects of ZJ43 were blocked by the group II mGluR antagonist LY341495 (1 mg/kg, i.p., n = 24).