Behavioral and neuroendocrine responses to alarm pheromone in Zebrafish
LE3 .A278 2011
Bachelor of Science
Relaxin-3 is a highly conserved member of the relaxin family of peptides; it is also highly concentrated in the midbrain tegmental region known as the nucleus incertus (NI) (Burzain et al., 2002). Several studies using rodent models of stress have indicated NI neurons are activated by physical stress treatments; these neurons also increase relaxin-3 expression after stress treatment (Banerjee et al., 2010; Tanaka et al., 2005). Given relaxin-3’s highly conserved structure and localization, its function is likely conserved across vertebrate species. This study extends the relaxin-3/stress hypothesis to an emerging model of vertebrate behavior and physiology; the zebrafish (Danio rerio). The present study uses a popular zebrafish stress test (Novel Tank Diving Test adapted from Egan et al., 2009) to identify behaviors that are affected by exposure to an alarm pheromone. Fish exposed to alarm pheromone are expected to engage in longer and more frequent freezing durations, longer latency to enter the top half of the test tank, and decreased frequency and duration spent in the top half of the tank. Previous studies indicate behavioral effects of alarm pheromone are short-lived (less than 30 minutes), but the present study demonstrates fish exposed to alarm pheromone (N=10) engage in significantly longer freezing durations than control fish (N=7) (p<0.05); this effect lasts as long as 45 minutes post-treatment. The current study predicted that exposure to alarm pheromone would increase neural activity in the NI of zebrafish, measured by cFos immunostaining. Technical difficulties resulted in poor staining results and therefore not analyzed. Suggestions to improve staining results, and why the present study found long-lasting behavioral effects are discussed.
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