Abstract
Mushroom bodies (MBs) formed via sequential birth of five classes of Kenyon cells (KCs) are essential for normal olfactory learning in Drosophila adults. Without knowing the type of neurotransmitter(s) released by KCs, MB outputs have been shown to be required for the retrieval of short-term memory. Here, using genetic reporters together with a total counting method, I determine how many KCs are cholinergic and how many are GABAergic in each of the five KC classes. Using nuclear localization green fluorescent protein (nls-GFP) as a reporter, I found that a MB has about 2700 KCs composed of roughly 870 γ neurons, 420 α’/β’ neurons, 90 pioneer α/β neurons, 480 early α/β neurons, and 860 late α/β neurons. I also found that most KCs are cholinergic while some KCs may be both cholinergic and GABAergic. To ameliorate brain neurodegenerative diseases, I tested if the steroid hormone 20-hydroxyecdysone (20E) has a mitogenic effect on KCs in Drosophila adults. After feeding 20E for 5 days, the total number of α’/β’ neurons increases nearly 20%, γ neurons decreases about 10% while the other three KC classes show slight changes. The implication of mitogenic manipulation of brain cells to ameliorate aging related memory loss and brain neurodegenerative diseases are discussed.