Vasopressin in the lateral septum promotes elemental conditioning to the detriment of contextual fear conditioning in mice

Previous experiments using a classical fear conditioning paradigm have prov ided evidence that the processing of contextual conditional stimuli (CSs) b y the hippocampus would be controlled by the amygdala through a modulation of hippocampal-lateral septal (H-LS) excitability. More specifically, our s uggestion was that vasopressin release into the LS would occur in an elemen tal conditioning case [pairing CS-CIS (unconditional stimulus) procedure] a nd would result in less hippocampal-dependent contextual stimuli processing (i.e. overshadowing of CSs by the simple CS). Conversely, when an unpairin g CS-US procedure is used, this would result in more contextual stimuli pro cessing through a decrease in vasopressin release into the LS. The aim of t he present experiment was to test this hypothesis using intraseptal injecti on of vasopressin or its V1/V2 antagonist. In agreement with this hypothesi s, results suggest that vasopressin release into the LS would constitute a device by which priority is given to the more salient simple stimulus to th e detriment of contextual information.