Intra- and interstrain differences in models of "behavioral despair"

In the present studies, base line and drug-induced performance of two mouse strains (C57Bl/6 and NIH-Swiss) was evaluated in the forced swim test (FST ) and tail suspension test (TST). Intra- and interstrain comparisons indica te that the biological substrates mediating performance in these behavioral procedures are not identical. For example; in NIH-Swiss mice, a sevenfold difference in base line immobility was observed between the FST and TST. By contrast, the base line immobility in C57Bl/6 mice was similar in both pro cedures. Further, in C57Bl/6 mice, imipramine produced a "U-shaped" dose-re sponse curve in the FST whilst no evidence of a biphasic response was prese nt in the TST at doses up to 45 mg/kg. In the FST, the AMPA receptor potent iator LY451646 produced a similar dose-response relationship in C57Bl/6 and NIH-Swiss mice, but the minimum effect dose (MED) was fivefold higher in N IH-Swiss mice. This potency difference appears due to both pharmacokinetic and pharmacodynamic factors. These intra- and interstrain differences in pe rformance indicate that despite a face value similarity, the neurochemical pathways involved in mediating performance in these two widely used tests a re not identical. (C) 2001 Elsevier Science Inc. All rights reserved.