Preliminary Examination of Infralimbic Activation in the Prefrontal Cortex in Fear Conditioned 129S1 and C57B6 Mice
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Deficits in extinction learning lead to maladaptive behavior such as generalized or persistent fear and are viewed as models of generalized anxiety or post-traumatic stress disorder. Previous work has identified several wild-type inbred mouse strains that differ in their capability for fear extinction learning. Specifically, they have found that the 129- inbred mouse strain is significantly impaired in extinction learning relative to the C57BL/6 mouse strain. Leveraging this phenotypic distinction between the strains enabled this study to examine the neurophysiological underpinnings of fear extinction learning in a mouse model that parallels many fear disorders. It was hypothesized that the 129-strains and C57BL/6 differ in the level of neuronal activation within the medial-prefrontal cortex. This brain region contains a subset of neurons that are active during acquisition learning and extinction learning. To test this hypothesis an immunohistochemically comparative assay took place. Examination of the strains neural activity in comparison to days of extinction training (0, 1, or 3) provided insight to the strains ability to learn to extinguish fear. This study looks at a sample population from a larger study. The preliminary quantification of neural activity indicted that the regions associated with extinction were not necessary or sufficient in extinction learning. To measures the difference in medial prefrontal cortex of 129S1 and C57BL/6mice neural counts were obtained via immunoreactivity for expression of immediate early genes (cFos, Zif268). The overall trend in immunoreactivity showed activation mediated extinction learning. The higher the regional activation the more learning occurred.