Behavioral effects of cyclazocine on rats assessed in the open field and residential maze

Abstract

Changes in behavior of rats caused by different doses of cyclazocine (0.2, 0.4, 0.75, 1.5, and 3.0 mg/kg) were detected by two different methods: the open field and the residential maze. In the residential maze the locomotion was recorded automatically, whereas in the open field the measurements were made by direct observation. In the maze low doses of cyclazocine (<1.5 mg/kg) caused a marked change in the time course of locomotion and local activity at the beginning of the 23-h sessions. The duration of this effect was dose-dependent, between 2 and 4 h. The highest dose (3 mg/kg) induced a strong stimulation of locomotor activity which lasted about 1 h, and stereotyped patterns, i.e., long periods of unidirectional runs through circular alleys. In the open field rearing and grooming behavior proved to be the most sensitive parameters. The frequency of both was reduced at a dose of 0.4 mg/kg. Locomotion showed the highest values at 1.5 mg/kg and decreased with the highest dose (3 mg/kg) to control levels. The study demonstrated that the principal changes induced by cyclazocine were of a qualitative nature, characterized by monotonous locomotor activity. The computerized residential maze procedure proved to be well suited to detect and quantify this behavioral change.