Simultaneous monitoring of conditioned place preference and locomotor sensitization following repeated administration of cocaine and methamphetamine.

The paradigm of conditioned place preference has been widely used to demonstrate the rewarding properties of psychomotor stimulants. Such drugs also stimulate locomotor activity. Repeated administration of low doses of psychomotor stimulants causes progressive increases in the locomotor stimulating effect, a phenomenon termed behavioral sensitization. Using a new activity monitor (SCANET MV-10LD) that simultaneously measures the amount of time spent and the distance traveled in each side of a two-compartment chamber, the present study assessed place preference conditioning and locomotor sensitization following repeated administration of cocaine or methamphetamine (MAP) in mice. We examined the effect of environmental factors on these activities using two different types of chamber: one having a single cue, and the other having dual cues for the discrimination of compartments. In both types of chamber, cocaine (5-20 mg/kg) and MAP (1-2 mg/kg) similarly produced conditioned place preference. However, repeated cocaine administration caused the development of locomotor sensitization only in the single-cue chamber. On the other hand, repeated administration of MAP resulted in the development of sensitization in both types of chamber. The findings indicate that environmental factors differentially affect the development of locomotor sensitization, but not place preference conditioning, following repeated administration of cocaine or methamphetamine. The advantages of this new system will be discussed.