Neural Activation in Rhagoletis Flies: Using Immunohistochemistry to Identify Glomerular Responses to Odor Stimuli.

Abstract

   Understanding how the brain processes sensory information is fundamental to the study of neurophysiology and behavior. Over evolutionary time, Rhagoletis fruit flies have diverged in their preferences for host fruits and odors. For these experiments, Rhagoletis pomonella flies were employed to examine the differences in the way insects respond to attractive versus aversive odor stimuli within the antennal lobe of their brain. 

   Previous studies have identified which regions are activated in the presence of butyl hexanoate and 3-methyl-1-butanol, the preferred odors of the apple and hawthorn variants, respectively. Trials with these odors are replicated in this study, along with linalool, a neutral odor, and 1-octen-3-ol. It is hypothesized that the latter odor should be unpleasant to apple and hawthorn races but appealing to the dogwood flies which are the next most closely related variant. 

    Using immunohistochemistry, we applied an antibody for phosphorylated extracellular signal-regulated kinase (pERK), aiming to stain the activated brain regions corresponding to each of the four odors.  Preliminary trials performed with nC82, DLG4 and Synorf antibodies determined that Synorf produced the highest resolution image of all the fruit fly’s brain, allowing for sharp visualization of the glomeruli within the antennal lobe. Thus, we decided that it will be used along with the pERK to stain the brains after odor stimulation.  By completing this project, we can then connect what is going on in the brain with the preference behaviors that they show in nature.

   This research was supported by NSF award # OIA-2242771.