2023 60 B3

Immunohistochemistry Used to Identify Neurons Involved in Pain Signaling in the Model Organism, Manduca sexta

By: Negeen Mostarshed

Department: Biology

Faculty Advisor: Dr. Megumi Fuse

Researchers report that over 50 million people experience chronic pain, which taxes the health care system, results in billions of dollars in lost revenue, and results in long-lasting debilitation and often death. We use a simpler model organism, such as the caterpillar, Manduca sexta, which displays defensive behavior post-injury, to investigate the mechanisms of pain in the form of nociception and sensitization. Previous electrophysiological studies suggest that the state of sensitization in M. sexta is encoded at the level of the central nervous system, however the neurons that mediate this behavioral plasticity remain unknown. We aim to visualize second order neurons in the CNS expressing immediate early genes in response to nociceptive stimulation using methods of immunohistochemistry on the CNS of injured and naive animals. We will assess the extent of pERK expression - the signaling molecule that triggers the expression of immediate early genes - alone or in the presence of a pERK inhibitor, in naive and sensitized larvae. We hypothesize that the CNS of sensitized animals will display more intense fluorescent signals while the pERK inhibitor will inhibit sensitization and therefore show less intense signaling. This data will help characterize the neural circuitry that mediates the defensive strike in M. sexta and help to prove that nociceptive sensitization is mediated by changes in the CNS.