"Sniff, sniff, good!" Dr. Yoshihiro Yoshihara Head, Laboratory for Neurobiology of Synapse Whether it is the fresh scent of young leaves in early summer, the sweet smell of fragrant olives in autumn, the rich aroma of coffee in the morning, or the mouthwatering, juicy smell of grilled beef, we all unconsciously enjoy a variety of odors via the functioning of the olfactory system. We, the members of the Laboratory for Neurobiology of Synapse, enjoy a life of study of the olfactory system by consciously making full use of our brains and bodies. Now, the story of olfaction and life will begin.... There is No Significant Difference Between Humans and Paramecia Olfaction and gustation are collectively called chemical senses. We start an action by receiving and sensing various chemical substances through the nose or mouth that come from outside. The mechanism is not much different from that of paramecia. Paramecia are not able to see or hear, but they can smell. When they sense chemical substances coming from matter that is vital to their existence (food, etc.), they start to move in its direction crying joyfully, "Sniff, sniff...good! I likeitlikeitlikeit!" (possibly). And if they sense a chemical substance that is generated by something dangerous to them, they scream "Noooo!, I hateithateithateit!" and run away (muchlike I do). Given these reactions, we find that chemoreception is evolutionarily the oldest sense. The Fly: One Tenth the Number of the Mouse As a child, a familiar summer scene for me was fighting off the ambush of flies that punctually attacked my lunch. This behavior was no doubt helped by their keen olfactory senses. The fly is a model creature for genetics, or forward genetics, that provides us with a royal road beginning with the search for mutants through to finding causal genes. A number of research studies on mutants, which are incapable of retaining a memory of odors, have been reported and the genetic cascade of olfactory memory analyzed. A recent remarkable study revealed that information about odorants, which flies receive, is transferred to the brain via certain neuronal pathways and the information is handled in a certain way. Surprisingly enough, the mechanism is quite similar to our mammalian mechanism. The fundamental principle behind the wiring pattern among neurons is identical and the number of odorant receptors in the fly or the number of glomeruli in the olfactory bulb is as small as one tenth those of the mouse. This proves that the fly is the most suitable model for olfactory research. So the study on flies is very important, isnﾕt it, Dr. Miura? What is the Fate of a Mouse that is Unable to Smell? What rings a bell with the term "mouse" is reverse genetics! A typical model is a "knock-out" mouse. By creating mice devoid of specific genes through genetic engineering techniques, we can infer the geneﾕs function from an analysis of its phenotype. The mouse earns a credit in olfactory research as well. One of the examples is the "knock-out" mouse which was created so that it lacks a particular gene (adenylyl cyclase III), which assumedly plays an important role in the olfactory sensory neurons during conversion of odorant molecules into electrical signals. These mice died immediately after they were born. No milk was found in their stomachs. They starved to death because they could not smell their motherﾕs nipples. That was the fate of the poor creatures. Dysosmia or olfactory disorder is a matter of life or death to mice. So the research with mice is very important, isnﾕt it, Dr. Itohara? The Nose of the Researcher Now the serious time (more serious I mean -I have been serious, havenﾕt I?). Any researcher must acquire an especially sharp sense of smell, but you donﾕt need to be a perfumer. You simply need a critical sense of smell that allows you to detect and precisely select the information that is most important and critical to your research, from among the countless presentations at the Society for Neuroscience. It is the nose that ensure that you do not miss the real treasures among the daily experimental results that may often seem strange and undecipherable. Sharpen your nose for creative research! Me? Well, unfortunately mine suffers from hay fever and...SNEEZE! Excuse me!