Neuroplasticity in olfactory sensation

The ability to detect volatile molecules in the environment is essential to the survival of countless organisms in that it is intimately involved in processes such as nourishment, the identification of predators or prey, reproduction and other manners of self-preservation. Much work has been performed to identify the key molecular components in olfactory sensory neurons that serve to detect these molecules and convey signals to the higher brain where structures including the olfactory bulb and cortex function to identify and remember these molecules. Furthermore, the topographical map of connections between the array of olfactory sensory neurons in the nose and the olfactory bulb has become the subject of much interest in that it helps explain how a given molecule, or odorant, produces a unique pattern of brain activity to generate it's signature. Less is known, however about the possibility that the olfactory sensory neurons themselves play an active role in the process of identifying and remembering odorants. In the process of my dissertation research I have uncovered a new physiological function of olfactory sensory neurons, and the molecular signaling events that support it, that helps explain how an animal can optimize its ability to sense and remember odorants that it encounters frequently, and as such are likely to be important for its survival.; Olfactory neurons can be sensitized to odorants by repeated exposure, suggesting that an animal's responsiveness to olfactory cues can be enhanced at the initial stage of detection. However, because olfactory neurons undergo a regular cycle of apoptosis and replenishment from precursor cells, the advantage of sensitization would be lost without a mechanism for odorant-enhanced survival of olfactory neurons. I have found that simple exposure of an animal to an odorant produces rapid activation of the Mitogen-activated Protein Kinase cascade, leading to Cyclic AMP Response Element-mediated transcription, and that activation of this pathway leads to an enhancement of olfactory neuron survival. This may represent a mechanism by which animals can enhance their ability to sense molecules in the environment that are crucial to their survival.