Formation of neuronal circuits is a dynamic process of rapid and concurrent formation and elimination of synaptic connections. During this early development immature neuronal networks typically display spontaneous, rhythmic activity, which is thought to be instrumental in development of the circuitry. How exactly activity shapes synaptic connectivity during development and the molecular mechanisms underlying these processes are not fully understood. The key questions focus on the cellular and molecular mechanisms that link electrical activity to changes in the structure and function of immature synapses and how these are regulated during development. To shed light on these mechanisms, we focus on the development of glutamatergic circuitry in the limbic system, and in particular, on the role of ionotropic glutamate receptors in this process. We aim to understand how the fast Hebbian and the slow, homeostatic plasticity mechanisms operate in the developing circuitry and how they control the transition from immature to mature type synaptic and circuit function. In addition, we are interested to understand how genetic and /or external disturbance influences developmental fine-tuning of the limbic networks and how aberrant development may affect behavior and vulnerability to neuropsychiatric disorders later on in life. Our experimental approach involves the use of in vitro electrophysiological techniques in combination with pharmacological and local genetic manipulation in various neuronal preparations.