The maturation of GABAergic circuitry in ferret visual cortex

Experience plays a critical role in maturation of cortical circuits. In visual cortex, experience-dependent development has been linked to the maturation of inhibitory interneurons. Parvalbumin-containing (PV) interneurons, a subtype of GABAergic interneurons, play an important role in cortical circuit function; however, it remains unknown how visual experience shapes their organization. We used immunohistochemistry to observe the organization of PV expression in visual cortex through visual maturity. Before visual experience, PV cell bodies and processes are most pronounced in layer 5, less in layer 2/3, and generally lacking in layer 4. Within 3 days of the onset of visual experience, PV organization undergoes a major shift, with PV expression found throughout layers 2-6. We performed dark rearing which determined that these morphological changes are due to visual experience. This rapid change in parvalbumin organization may play a role in functional changes associated with the onset of visual experience.