The effects of water deprivation on conditioned freezing to contextual cues and to a tone in rats

In two experiments we used an automated system for quantifying freezing res ponses in rats to replicate and extend Maren et al. (Maren S, DeCola JP, Fa nselow MS. Water deprivation enhances Fear conditioning to contextual, but not discrete, conditional stimuli in rats. Behav Neurosci 1994;108:645-9: M aren S, DeCola JP, Swain RA, Fanselow MS, Thompson RF. Parallel augmentatio n of hippocampal long-term potentiation, theta rhythm and contextual fear c onditioning in water deprived rats. Behav Neurosci 1994:108:44-57) who foun d that water deprivation in rats produced a selective enhancement in condit ioning to context. as opposed to conditioning to a tone. In experiment 1 we gave water deprived and non-deprived rats either three or ten pairings of a tone and foot shock. During conditioning water deprivation decreased over all freezing only in rats that received ten pairings. On 2 subsequent days we assessed conditioned freezing (1) to the contextual cues of the conditio ning chamber and (2) to the tone when presented in a distinctive, novel env ironment. We found, in direct contrast to Maren et al, (Maren S, DeCola JP, Fanselow MS. Water deprivation enhances fear conditioning to contextual, b ut nut discrete, conditional stimuli in rats. Behav Neurosci 1994,108:645-9 ), that (a) water deprived rats did not differ from non-deprived rats in le vels of conditioned contextual freezing and that (b) water deprived rats di d show reduced levels of freezing to the tone stimulus. In the same experim ent we found that the number of tone-shock pairings did not affect levels o f conditioned contextual freezing but that rats that had received three pai rings did show reduced levels of freezing to the tone stimulus compared wit h rats that had received ten pairings, thereby demonstrating that the behav ioural procedure and analysis system that we used was appropriately sensiti ve to differences in conditioning. In experiment 21 therefore, we sought to replicate Maren et al. (Maren S, DeCola JP: Fanselow MS. Water deprivation enhances fear conditioning to contextual, but not discrete, conditional st imuli in rats. Behav Neurosci 1994;108:645-9) using, as far as possible, ex actly the same procedural parameters. Here we found that water deprivation produced no effects on conditioned freezing to the contextual cues or to th e tone. We conclude that there is sufficient reason to doubt the generality of the previously reported findings. (C) 2001 Elsevier Science B.V. All ri ghts reserved.