PT  - JOURNAL ARTICLE
AU  - Ariel Agmon
AU  - Greg Hollrigel
AU  - Diane K. O’Dowd
TI  - Functional GABAergic Synaptic Connection in Neonatal Mouse Barrel Cortex
AID  - 10.1523/JNEUROSCI.16-15-04684.1996
DP  - 1996 Aug 01
TA  - The Journal of Neuroscience
PG  - 4684--4695
VI  - 16
IP  - 15
4099  - http://www.jneurosci.org/content/16/15/4684.short
4100  - http://www.jneurosci.org/content/16/15/4684.full
SO  - J. Neurosci.1996 Aug 01; 16
AB  - Intracortical inhibition is crucial to proper functioning of the mature neocortex, yet, paradoxically, is reported to be rare or absent in the neonatal animal. We reexamined this issue by recording whole-cell postsynaptic currents (PSCs) of barrel cortex neurons in thalamocortical brain slices from neonatal mice. Monosynaptic, excitatory thalamocortical responses were elicited in layers V/VI neurons as early as postnatal day 0 (P0, the first 24 hr after birth) and in presumptive layer IV as early as P2. At very low stimulation frequencies, the monosynaptic response was invariably followed by a prolonged (up to 1 sec) synaptic barrage, which fatigued at stimulus repetition rates of 2/min or higher. This barrage consisted of postsynaptic responses to spiking activity in neighboring cortical cells, because (1) it could also be evoked by intracortical stimulation in coronal slices and (2) it was abolished by antagonists to NMDA receptors (NMDARs), even when NMDARs on the recorded cell were under a voltage-dependent block. Some of the larger polysynaptic events changed polarity at a negative reversal potential and were blocked by GABAA receptor (GABAAR) antagonists, with a concurrent enhancement of the extracellular field potential, indicating that they were GABAAR- mediated, Cl-dependent inhibitory PSCs (IPSCs). We conclude that a network of functional intracortical GABAAR-mediated synaptic connections exists from the earliest postnatal ages, although it gives rise to responses that differ from mature IPSCs in reversal potential and latency.