The Structural Basis Of Mammalian Olfactory Learning And Memory

The olfaction is a kind of most ancient sensory. In the long history of evolution, mammals have extraordinary and powerful ability of odor perception and olfactory learning and memory. Except the numerous odor receptor genes, there are many intricate neural circuits and no more than three synapses to the central areas related to the emotion and cognition, and each area processing olfactory information receives mass of centrifugal inputs from other regions and various modulate inputs from the brain stem.Plasticity of neural circuits is the basis of learning and memory. Synaptic plasticity is the core of entire neural circuit plasticity. Thus, it is important to reveal the synaptic structural basis of olfactory learning and memory and related neural circuits for clarifying the learning and memory mechanisms. We use the methods of plasmid electroporation and excitatory and inhibitory synaptic protein labeling with adopting anosmia transgenic mice, and found that the excitatory synaptic inputs from projection neurons and inhibitory synaptic inputs from the deep short axon cells onto the granule cells, the most common interneurons in olfactory bulb, have the potential of structural plasticity, rather than the centrifugal inputs from the olfactory cortex. So, the inhibitory and dendrodendritic synapses of granule cells could be the sites of memory storage.In addition, long-term memory formation, consolidation and storage need new protein synthesis to participate in the construction of new synaptic connections. CREB (cAMP response element-binding protein) is an important transcription factor to mediate synaptic plasticity and intrinsic plasticity. It is impossible to assess the regions and even the neuron types related to memory, but also the neural circuits in the overall brain through examining the changes of the pCREB. Therefore, we study the spacial and temporal characteristics of pCREB in major regions related to olfaction after odor-reward associative learning, and found that the dynamics of pCREB were very significantly different in different regions and at different time. The data we got supply the potential targeted basis to mediate odor perception and olfactory learning and memory.