Fig. 4

The time course of the change in neural intracellular Cl⁻ concentration during early developmental periods. a During the embryonic and early neonatal periods, NKCC1 is more active than KCC2 and the reversal potential for Cl⁻ is maintained above the resting potential. However, at the birth, maternal oxytocin acts on the fetal neurons and suppresses NKCC1 activity resulting in a transient hyperpolarizing shift of Cl⁻ reversal potential. After birth, KCC2 becomes gradually more active than NKCC1 and the Cl⁻ reversal potential finally becomes more negative than the resting potential. Failure of sufficient oxytocin action at birth has been suggested to be a cause of pathological conditions such as autism spectrum disorders. b Responses to GABA and glycine change from excitatory to inhibitory between the 1st and the 2nd postnatal weeks due to the increase of intracellular Cl⁻ concentration