Corticosteroid effects on glutamatergic transmission and fear memory

In our daily life we are regularly exposed to situations which we experience as stressful. In response to these events our body increases the release of corticosteroid hormones from the adrenal glands. These hormones promote behavioural adaptation to stressful experiences by enhancing the storage of relevant information and by adjusting strategies that can be used to solve problems. An important question is how these hormones enhance learning and memory.
The current view of how memories are formed is that neurons are activated during learning, resulting in long-term changes in communication between neurons. At the junctions between neurons - synapses - AMPA receptors mediate synaptic transmission and NMDA receptors are relevant to initiate changes in synaptic transmission. AMPA receptors are mobile and the number of AMPA receptors at synapses is precisely regulated. The trafficking of AMPA receptors to and from synapses - initiated by NMDA receptors - is critically involved in synaptic function and memory formation.
The overall aim of this thesis was to examine how corticosteroid hormones regulate synaptic transmission and whether this is important for the formation of fear memories. We report that corticosteroid hormones regulate the function, mobility, and expression of AMPA receptors, and retention of AMPA receptors at synapses is critical for the memory enhancing effects of stress. In addition, we find that corticosteroid hormones enhance the function of NMDA receptors. Together these studies reveal novel insights into the mechanisms that underlie the acquisition and storage of fear memories.