Exploring Cholinergic Mechanisms in Hydra through Pharmacological Intervention and Behavioral Observation

Efforts to uncover a cholinergic neurotransmission system in Hydra have yielded conflicting results, where early studies suggested cholinergic agents affect the animal’s movement and later studies failed to reproduce these results. The identification of cholinergic mechanisms in the Cnidarian Nematostella vectensis and the presence of nicotinic Acetylcholine receptor (nAChR)-like sequences in the published Hydra genome have led us to revisit this issue. This study explores cholinergic mechanisms in Hydra through a comprehensive approach, including bioinformatics analysis, dose-response experiments, live-neuron imaging, and molecular approaches. Bioinformatics analysis identified 6 homologous nAChR sequences, one of which was confirmed by RT-qPCR. Dose-response experiments clearly showed that cholinergic agonists induced wholebody contractions and a nAChR antagonist sequestered this response. Live neuron imaging confirms that agonist treatment plays a role in neuron excitation that directly precedes behavior. Overall, my results confirm the existence of cholinergic mechanisms in Hydra. Further investigations can prove a direct or indirect mechanism of action on neurons.