The Effect of Bacterial Lipopolysaccharides on Immune Function and Adult Neurogenesis in the cricket, Acheta domesticus

Abstract

Neurogenesis is the phenomenon in which the brain produces new neurons. Neurons, which are located in the brain and spinal cord, are especially important to an organism’s function, as they allow for communication and information processing. Although the exact function of neurogenesis is unclear, recent studies suggest its importance in learning and memory. As a whole, our lab investigates the factors that can affect neurogenesis, such as environment and behavior. My study specifically looked at how the immune system of an organism could affect adult neurogenesis. We chose to look at immune function because many studies have linked immunocompetence to neurogenesis in vertebrate animals; it is our goal to investigate this relationship in an invertebrate model, the house cricket Acheta domesticus. To activate the immune system, we injected experimental crickets with bacterial lipopolysaccharide (LPS). We compared immune activity and neurogenesis between experimental and control crickets. The cricket model was chosen because crickets have relatively simple immune and nervous systems which are easy to manipulate. Going further, they also have adult neurogenesis in brain regions functionally similar to those of mammals. We found that crickets treated with LPS exhibit a change in immune function, as shown by a decrease in phenoloxidase (an enzyme important in insect immune function) activity levels, a decrease in survival rate, and an increase in nodule number and size. We found inconclusive results on the effect of LPS injection on neurogenesis due to low sample sizes.