Effect of long term baclofen treatment on recognition memory and novelty detection

Abstract

We studied the effect of long term baclofen treatment on recognition memory and novelty detection in rats using a habituation paradigm in an open field setting. Rats pretreated with 3 weeks' daily baclofen injection (0, 2 and 5 mg/kg) were tested in four 10 min sessions (familiarization session and three testing sessions: S 1, S 2 and S 3), with 10-min intersession intervals. During S 1, S 2 and S 3, rats were repeatedly exposed to the same two odor stimuli. During S 3, for half of the rats in each treatment group, the spatial locations of the two stimuli were switched (Change) and for the other half the stimuli were replaced in the same locations (No Change). Two habituation scores were measured for each subject: H 1 = N 1 − N 2; H 2 = N 2 − N 3 ( N i the number of contacts made during S i). Baclofen at the highest dose (5 mg/kg) reduced the amount of habituation between S 1 and S 2 ( H 1) and increased responses to novel spatial arrangement, measured as the difference between H 2 for the No-Change and Change groups. These results suggest a simultaneous impairment of recognition memory and enhancement of spatial novelty detection.