(full paper is archived in the Miller Library)
Title: Propranolol affects spatial memory and anxiety in zebra fish (Danio
Student Author(s): Cooper, Holly C.
Faculty Advisor(s): Thompson, Stuart
Location: Final Papers Biology 175H
Date: June 2008
Abstract: Propranolol is a non-selective ß-blocker that has recently proven useful in the treatment of social anxiety and Post Traumatic Stress Disorder. Recollection of a memory requires that the memory pathway is strengthened by continual re-visitation. This re-visitation requires the activation of β-adrenergic receptors by catecholamines such as epinephrine and norepinephrine, two important signalers in the fight-or-flight stress response. Propranolol blocks this activation and thus prevents the strengthening of memory pathways. Most previous studies have utilized either human or rodent study subjects. Zebra fish provide a unique opportunity to examine an organism with a different scale of neuro-complexity and a more accessible genome, which could eventually lead to a greater understanding of how the β-receptor memory coupling functions. The fish (Danio rerio) were trained to associate tapping on the glass of their aquarium with a positive (Tap+Food), negative (Tap+Net), or neutral experience (Tap). The control fish (No Tap) were not exposed to tapping during the three week training process. After re-activation of the memory, propranolol was dissolved in the water for an overall concentration of 27μM. The anxiety levels and memory retention of the fish were then tested after 1, 2, 3 and 18 hours. Preliminary data suggest that propranolol has a clear impact on the anxiety levels of the negative, neutral and control fish and may have some impact on the positive fish. Additionally, propranolol decreases the clarity and accuracy of spatial memory in fish trained using positive reinforcement. This study demonstrates that β-receptors and memory recall are tightly coupled throughout evolution, despite differences in neuro-complexity. Future studies should utilize a larger number of replicates to yield statistical significance and a slightly lower concentration of propranolol as 27μM seems to be at the threshold of toxicity in these fish.