Fig. 2.
Locomotor activity after subcutaneous administration of heroin (A), 6-AM (B), and morphine (C) to mice pretreated with saline or (+)-naloxone (0.01, 0.1, 1, 10, or 50 mg/kg, s.c.). Locomotor activity is given as run distance in centimeters versus time curves at 5-minute intervals (means) (left) and as the maximal distance run (Emax) in centimeters in a 5-minute interval (means + S.E.M.) (right). n = 6–8 in each group. *P < 0.05 (Mann–Whitney U test compared with the saline-pretreated group).