The development of parvalbumin-positive neurons 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 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.