Jeff Beardsall

Degree: Bachelor of Science with Honours in Psychology

Supervisor: Dr. Peter McLeod and Dr. Brian Wilson

Title: Behavioural and Physiological Responses to Alarm Pheromone in Zebrafish (Danio rerio)

Abstract:  Vertebrates undergo several characteristic physiological changes in response to stressful stimuli (commonly referred to as the “fight or flight response”). These changes are mediated by neural and endocrine systems. The neuroendocrine hypothalamic-pituitary-adrenal (HPA) axis in mammals, and the equivalent hypothalamic-pituitary-interrenal (HPI) axis in teleost fish, increases circulating cortisol levels. Cortisol liberates and allocates energy resources that the serve metabolic requirements of the fight or flight response.  The signaling cascade in the HPA axis is well understood, but several rodent-based studies employing physical stressors indicate a newly discovered neuropeptide may also be involved in mediating the mammalian stress response.

Relaxin-3 is highly expressed in the dorsal tegmental region in the mammalian midbrain. This region receives sensory afferents from many visceral organs, and projects to several areas including the hypothalamus and amygdala. This study extends the relaxin-3/stress hypothesis to a highly-versatile vertebrate model; the zebrafish (Danio rerio).  The current study uses a naturally occurring “alarm pheromone” to elicit a stress response in zebrafish. Behavioural results indicate freezing behavior is significantly increased in pheromone-treated fish (n=12) compared to control group (n=11). If pheromone-treated fish demonstrate increased neural activity in relaxin-3 positive areas there will be evidence for relaxin-3’s role in vertebrate stress response.