RT Journal Article
SR Electronic
T1 A Role for Silent Synapses in the Development of the Pathway from Layer 2/3 to 5 Pyramidal Cells in the Neocortex
JF The Journal of Neuroscience
JO J. Neurosci.
FD Society for Neuroscience
SP 13085
OP 13099
DO 10.1523/JNEUROSCI.1262-12.2012
VO 32
IS 38
A1 Paul G. Anastasiades
A1 Simon J. B. Butt
YR 2012
UL http://www.jneurosci.org/content/32/38/13085.abstract
AB The integration of neurons within the developing cerebral cortex is a prolonged process dependent on a combination of molecular and physiological cues. To examine the latter we used laser scanning photostimulation (LSPS) of caged glutamate in conjunction with whole-cell patch-clamp electrophysiology to probe the integration of pyramidal cells in the sensorimotor regions of the mouse neocortex. In the days immediately after postnatal day 5 (P5) the origin of the LSPS-evoked AMPA receptor (AMPAR)-mediated synaptic inputs were diffuse and poorly defined with considerable variability between cells. Over the subsequent week this coalesced and shifted, primarily influenced by an increased contribution from layers 2/3 cells, which became a prominent motif of the afferent input onto layer 5 pyramidal cells regardless of cortical region. To further investigate this particular emergent translaminar connection, we alternated our mapping protocol between two holding potentials (−70 and +40 mV) allowing us to detect exclusively NMDA receptor (NMDAR)-mediated inputs. This revealed distal MK-801-sensitive synaptic inputs that predict the formation of the mature, canonical layer 2/3 to 5 pathway. However, these were a transient feature and had been almost entirely converted to AMPAR synapses at a later age (P16). To examine the role of activity in the recruitment of early NMDAR synapses, we evoked brief periods (20 min) of rhythmic bursting. Short intense periods of activity could cause a prolonged augmentation of the total input onto pyramidal cells up until P12; a time point when the canonical circuit has been instated and synaptic integration shifts to a more consolidatory phase.