Molecular Mechanisms of Nicergoline from Ergot Fungus in Blocking Human 5-HT3A Receptor

This study investigates the modulatory effects of nicergoline, a major bioactive compound derived from ergot fungus, on the 5-hydroxytryptamine 3A (5-HT3A) receptor. Utilizing a two-electrode voltage-clamp technique, we evaluated the impact of nicergoline on the 5-HT-induced inward current (I_5-HT) in 5-HT3A receptors. Our findings reveal that nicergoline inhibits I_5-HT in a reversible and concentration-dependent manner. Additionally, the observed voltage-dependent and use-dependent inhibition indicates that nicergoline acts as an open channel blocker of the 5-HT3A receptor. To further elucidate the interaction between nicergoline and the 5-HT3A receptor, we conducted molecular docking studies. Overactivation of the 5-HT3A receptor can enhance excitatory neurotransmission, potentially leading to heightened anxiety and stress responses. It may also interfere with hippocampal functions, adversely affecting learning and memory. Additionally, exceed activation of these receptors is a primary mechanism underlying nausea and vomiting, commonly observed during chemotherapy or in response to certain toxins. Collectively, our results suggest that nicergoline has the potential to inhibit 5-HT3A receptor activity by interacting with binding residues L260 and V264. This inhibition may enhance cognitive function by stabilizing neural circuits involved in cognitive processes and can improve cognitive symptoms in patients with dementia. Additionally, the anxiolytic effects resulting from 5-HT3A receptor inhibition could promote overall psychological well-being in affected individuals. Thus, the role of nicergoline as a 5-HT3A receptor antagonist not only highlights its therapeutic potential but also warrants further exploration into its mechanisms and broader implications for managing neurodegenerative diseases.