Bursting mitral cells time the oscillatory coupling between olfactory bulb and entorhinal networks in neonatal mice

Abstract

Shortly after birth, the olfactory system provides to blind, deaf, non-whisking and motorically-limited rodents not only the main source of environmental inputs, but also the drive boosting the functional entrainment of limbic circuits. However, the cellular substrate of this early communication remains largely unknown. Here we combine in vivo and in vitro patch-clamp and extracellular recordings to reveal the contribution of mitral cell (MC) firing to the early patterns of network activity in the neonatal olfactory bulb (OB) and lateral entorhinal cortex (LEC), the gatekeeper of limbic circuits. We show that MCs predominantly fire either in an irregular bursting or non-bursting pattern during discontinuous theta events in OB. However, the temporal spike-theta phase coupling is stronger for bursting MCs when compared to non-bursting cells. In line with the direct OB projections to LEC, both bursting and non-bursting firing augments during coordinated patterns of entorhinal activity, yet to a higher magnitude for bursting MCs. These cells are stronger temporally coupled to the discontinuous theta events in LEC. Thus, bursting MCs might drive the entrainment of OB-LEC network during neonatal development. KEY POINTSO_LIDuring early postnatal development mitral cells show either irregular bursting or non-bursting firing patterns C_LIO_LIBursting mitral cells preferentially fire during theta bursts in the neonatal OB, being locked to the theta phase C_LIO_LIBursting mitral cells preferentially fire during theta bursts in the neonatal lateral entorhinal cortex and are temporally related to both respiration rhythm- and theta phase C_LIO_LIBursting mitral cells act as cellular substrate of the olfactory drive promoting the oscillatory entrainment of entorhinal networks C_LI