Effects of Diphenhydramine on Neurotransmitters, Neurons, and Memory in C. Elegans

Overview

Caenorhabditis elegans is a transparent, microscopic nematode with an entirely mapped neurological system. This allows for studies on neuronal activity as a simplified model of the human neurological system. Antihistamines have recently been linked to memory loss, specifically dementia, in humans. Last year, we performed an investigation behaviorally training C. elegans and exposing “trained” nematodes to antihistamines, hypothesizing behavior change and memory dysfunction would occur when the nematodes were exposed to the antihistamines diphenhydramine (Benadryl) and cetirizine (Zyrtec). The results implied that C. elegans became behaviorally trained to cease reacting to vibrations applied to the side of their petri dishes in short taps, then recommenced reacting to vibrations after exposure to antihistamines, indicating a possible loss of the memory of that training. This year, our experiment was based off this prior research. Two tagged strains of C. elegans, EAW113 (dop-1::gfp, dop-3::rfp) and EAW115 (unc-17::gfp, mod-1::mCherry), were synchronized to the L1 larval stage. The C. elegans were then conditioned to stop reacting to vibrations applied to the side of the dish with an electric toothbrush. This process was repeated for a total of 180 minutes over two days, resulting in the C. elegans showing signs of becoming conditioned to the vibrating “taps”, as indicated by a decline in the percentage of C. elegans responding to the vibrations. After conditioning, diphenhydramine (Benadryl) or sterile water was added to ensure direct exposure of the C. elegans. Groups exposed to diphenhydramine exhibited a loss of conditioned response of the behavioral training, while the control groups retained the conditioned response to the vibration stimulus. The EAW113 and EAW115 strains were utilized because they had specific neurotransmitter receptors tagged with either green fluorescent protein (GFP) or red fluorescent protein (RFP or mCherry). These receptors are for dopamine (dop-1 and dop-3), serotonin (mod-1) and acetylcholine (unc-17). This enabled us to directly observe specific neural receptor expression. Images taken using fluorescent microscopy indicated that C. elegans exposed to antihistamines ad lower levels of the neurotransmitters than control C. elegans. These findings correlate with previous data gathered from a nearly identical training and antihistamine exposure experiment performed on wildtype C. elegans. Results from both experiments suggest a link between antihistamines and behavior change or memory dysfunction in the nematode C. elegans.

Competition history

• AJAS 2019 Category not listed

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