Natural cortical neurons form functional networks through a complex set of developmental steps. A key process in early development is the transition of the spontaneous network dynamics from slow synchronous activity to a mature firing profile with complex high-order patterns of spikes and bursts. In the present modeling study we investigate the required properties of the network to initialize this transition by the shift of the chloride reversal potential, which switches the effect of the GABA synapses from depolarizing to hyperpolarizing. The simulated networks are generated by a statistical first-order description of parameters for the neuron model and the network architecture.