Professor Richmond Thompson
Joseph Adu, '07
This summer, I worked with Priscilla Chan in Professor Richmond Thompson's goldfish lab. Priscilla and I researched peripheral influences on social behavior in goldfish. Essentially, our lab proposed a model that says that behavior is a process in which the brain sends information to the periphery to change the current physiological state of the organism, then that information is relayed from the periphery back to the brain (via some kind of a feedback loop) and that influences how one behaves. The Thompson lab previously discovered that the presence of Vasotocin (VT) in the hindbrain leads to decreased social approach behavior and an increase in both ventilation and heart rate (peripheral physiological responses that may be related to anxiety); thus, VT is the major focus of the lab. VT is a major neuropeptide produced by cellsin the preoptic area and transferred down the axon to the hindbrain, where it is released by axon terminals. Those terminals wrap around cells that produce substance P (a neurokinin involved in nociception that also causes anxiety), which themselves send axons into the periphery. Similar to VT, SP was previously found to inhibit social approach behavior.
Although we knew that central VT influences peripheral physiological processes and social approach behavior, we also knew that VT is produced in the brain and not in the periphery; therefore, if VT was affecting peripheral processes, we needed to first find out what was mediating those effects. Essentially, we were in search of a possible pathway underlying the peripheral effects of VT. First, we explored the possibility that VT was carrying out its peripheral effects via interaction with SP cells in the hindbrain by testing whether SP evoked similar peripheral physiological responses as VT. We found that, similar to VT, SP also increased ventilation rate; therefore if SP was producing similar effects in the periphery as central VT, therefore suggesting that VT could be working through SP to carry out its peripheral effects. Secondly, we tested to see whether the autonomic system was a possible mediator of VT's peripheral effects and found that manipulations of the sympathetic branch of the autonomic nervous system yielded similar effects on social approach behavior as did VT and SP.
In conclusion, our results suggest that the peripheral effects of VT are being mediated by SP cells. These SP cells originate from the hindbrain and are strongly innervated by VT fibers; thus, VT could be influencing the SP cells, which then feed into the periphery to influence social approach behavior via the sympathetic branch of the autonomic nervous system (as suggested by results from our autonomic manipulations). In the future, we may need to replicate some of our experiments to strengthen our results and gain more statistical power. Summer research was a valuable experience for me, and I look forward to another opportunity to conduct more research.