Slip-down from a Raised Platform: Another Behavior of Slc:ddY Mice Treated with Methamphetamine

Abstract

Slip-down behavior from a raised platform of Slc:ddY mice was examined. Mice intraperioneally injected with 1 or 1.5 mg/kg of methamphetamine (MAP) slipped down from a raised platform of 10 cm diameter and 20 cm height within 5 min, 20 min after the injection. After pretreatment five times with 1 mg/kg MAP at intervals of 3 days, the slipdown was induced after injection of 0.5, 1 or 1.5 mg/kg MAP, but after pretreatment ten times with 1 mg/kg MAP at intervals of 3 days the behavior was not recognized at the same doses. These phenomena were like reverse-tolerance and tolerance. The situational change of the MAP treatments, placement on the platform after each pretreatment, did not affect the phenomena. The present findings strongly suggest that the slip-down is a behavior affected by the dose and number of administration of MAP, but not by the treatment situation. Key words: Slc:ddY mouse, methamphetamine, slip-down from a raised platform chased from Dainihon Seiyaku Co. Osaka, Japan. Physiological saline (PS), 200 µl , as a control or 0.5, 1 or 1.5 mg/kg of MAP were intraperitoneally respectively injected to one of four groups of 5 mice. Twenty minutes after the injection, each of these mice was placed on a raised platform (10 cm diameter, 20 cm height) and their behavior was investigated for 5 min. All of the mice moved about on the platform: forwards, backwards and changing body direction. Mice injected with PS or 0.5 mg/kg of MAP stopped at the edge of the platform, but mice injected with the 1 or 1.5 mg/kg MAP could not stop themselves at the edge and slippeddown from the platform within 5 min. None of the mice showed stereotypical behavior, sniffing and headbobbing, induced by MAP [4].