The effects of phencyclidine on fighting in differentially housed mice

The effects of phencyclidine (PCP) on the fighting of individually housed male mice were examined (1) after different lengths (5-35 days) of individual housing, and (2) in mice of different ages (35, 70 or 170 days old) at the onset of individual housing. Significant increases in the total time spent fighting in a 10-minute aggression test were observed at 19-21 and 32-35 days of individual housing with 1.25 mg/kg PCP and at 10 and 32-35 days with 2.50 mg/kg PCP. Relative to control groups, the percentage of mice fighting after 19-21 and 32-35 days of individual housing was significantly decreased with 2.5 mg/kg. At 1.25 mg/kg, PCP increased total fighting time and decreased the latency to the first fight in mice at 35 or 70, but not 170 days of age at the onset of individual housing. No increases in motor activity in individually housed mice were recorded at these doses. These results suggest that PCP may facilitate fighting in mice when individually housed for a minimum of 10 days.