The L-type voltage-gated calcium channel CaV1.3 mediates consolidation, but not extinction, of contextually conditioned fear in mice

Using pharmacological techniques, it has been demonstrated that both consolidation and extinction of Pavlovian fear conditioning are dependent to some extent upon L-type voltage-gated calcium channels (LVGCCs). Although these studies have successfully implicated LVGCCs in Pavlovian fear conditioning, they do not provide information about the specific LVGCC isoform involved. Both of the major LVGCC subtypes found in the brain (Ca(v)1.2 and Ca(v)1.3) are targets of the pharmacological manipulations used in earlier work. In this study, we used mice in which the gene for the pore-forming subunit (alpha(1D)) Ca(v)1.3 was deleted (Ca(v)1.3 knockout mice) to elucidate its contribution to consolidation and extinction of conditioned fear. We find that Ca(v)1.3 knockout mice exhibit significant impairments in consolidation of contextual fear conditioning. However, once sufficiently overtrained, the Ca(v)1.3 knockout mice exhibit rates of extinction that are identical to that observed in wild-type mice. We also find that Ca(v)1.3 knockout mice perform as well as wild-type mice on the hidden platform version of the Morris water maze, suggesting that the consolidation deficit in conditioned fear observed in the Ca(v)1.3 knockout mice is not likely the result of an inability to encode the context, but may reflect an inability to make the association between the context and the unconditioned stimulus.