Neuronal regeneration occurs naturally in a few restricted mammalian brain regions, but its functional significance remains debated. The vast majority of adult-generated interneurons in the Olfactory Bulb become granule cells. Interestingly, there are several physiological differences between immature granular cells and those that have matured and are stably integrated within the circuit. In fact, previous work has shown that the recruitment of synaptic inputs onto new granular cells occurs soon after they arrive in the Olfactory Bulb. However, little is known about the functional differences between granular cells born at different periods in the animal’s life.
In this study, the synaptic properties of adult-born granule cell interneurons integrated in the mouse olfactory bulb were assessed by optogenetically targeting newborn granule cells at different stages of its maturation. The authors found that the dendrodendritic interactions that adult-born interneurons establish whit resident mitral cells lack metabotropic GABAergic modulation. This is in contrast with the well-established presynaptic GABAB-mediated depression of GABA release observed in the dendrodendritic communication between mitral neurons and granule cells born just after birth. The lack of metabotropic GABAergic modulation of dendrodendritic interactions between mitral neurons and adult-born granule cells, correlates with the extrasynaptic localization of GABAB receptors in adult-born granule cells. These results indicate that adult neurogenesis produces a population of functionally unique GABAergic synapses in the olfactory bulb, suggesting that these newcomers may perform different computations to those similar neurons already residing in the circuit.
José María Cornejo Montes de Oca
Valley M, Henderson L, Inverso S, Lledo, P. (2013). Adult neurogenesis produces neurons with unique GABAergic synapses in the olfactory bulb. The Journal of Neuroscience, 33(37):14660–14665.