PARALLEL AUGMENTATION OF HIPPOCAMPAL LONG-TERM POTENTIATION, THETA-RHYTHM, AND CONTEXTUAL FEAR CONDITIONING IN WATER-DEPRIVED RATS

The influence of water deprivation on hippocampal long-term potentiati on (LTP), theta rhythm, and contextual fear conditioning in rats was e xamined. In Experiment 1, hippocampal EEG activity and perforant path LTP were assessed in pentobarbital-anesthetized rats. Water deprivatio n did not affect baseline cell excitability or low-frequency synaptic transmission in the dentate gyrus, but it increased the magnitude of p erforant path LTP and elevated the proportion of theta rhythm in the E EG. In Experiment 2, rats were classically conditioned to fear a novel context through the use of aversive footshocks. Water deprivation fac ilitated the rate of contextual fear conditioning but did not alter th e asymptote of learning. Experiment 3 demonstrated that the facilitati on of contextual fear conditioning was not due to a change in uncondit ional shock sensitivity. These results suggest that water deprivation exerts an influence on contextual fear conditioning by modulating hipp ocampal LTP and theta rhythm and that these processes serve to encode contextual information during learning.