Dose response effects of lithium chloride on conditioned place aversions and locomotor activity in rats

The present study examined the multi-variable locomotor activity effects of lithium chloride (LiCl) treatment in male rats. Of interest was a determination of which variables might show a dose-response relationship in LiCl-induced conditioned place aversions. Automated openfields were partitioned into two chambers distinct in tactile and visual cues. A control group [n = 8] received saline (NaCl; 0.15 M) paired with both chambers while three LiCl groups (0, 15 M; 32 mg/kg [n = 7], 95 mg/kg [n = 7], 127 mg/kg [n = 7]) received LiCl paired with the normally preferred chamber and saline paired with the non-preferred chamber. During extinction trials, rats were allowed to choose between the two chambers to provide an index of conditioned place aversions. Locomotor activity and its distribution within the chambers were also assessed during both conditioning and extinction trials. Dose-dependent decreases occurred in all measures of locomotor activity following LiCl administration during conditioning. During extinction trials, place aversions developed in animals conditioned with LiCl. LiCl-treated rats spent significantly less time in the LiCl-paired chamber relative to controls but not in a dose-dependent manner. Animals that had been conditioned with 95 or 127 but not 32 mg/kg LiCl, displayed significantly more vertical activity in the LiCl-paired chamber than controls during extinction trials. These findings indicate that, in addition to producing dose-dependent unconditioned effects on locomotor activity, LiCl also produces dose-dependent conditioned effects on vertical activity. These conditioned rearing response effects provide a valid measure of the conditioned avoidance response that provides evidence for dose-dependent LiCl-induced conditioned place aversions. (c) 2005 Elsevier B.V All rights reserved.