Huperzine AvsTianeptine

Huperzine A is a potent, selective, and reversible inhibitor of acetylcholinesterase (AChE), binding to the enzyme's active site and preventing hydrolysis of acetylcholine to choline and acetate. By blocking AChE, it increases acetylcholine concentration in the synaptic cleft, prolonging activation of muscarinic (M1-M5) and nicotinic receptors. Huperzine A also blocks NMDA glutamate receptors in a non-competitive, use-dependent manner (similar to memantine), binding to the phencyclidine site within the ion channel and protecting neurons from excitotoxic calcium influx. It shows selectivity for the NR2A and NR2B subunits. Additionally, huperzine A has antioxidant properties, scavenging reactive oxygen species and reducing lipid peroxidation. It may enhance NGF signaling.

Tianeptine is a full agonist at mu-opioid (MOR) and delta-opioid (DOR) receptors, mediating both its antidepressant/anxiolytic effects and abuse potential at high doses. Paradoxically, it enhances serotonin reuptake via SERT—opposite to SSRIs—yet still produces antidepressant effects, possibly through opioid-mediated mood regulation. Tianeptine modulates glutamatergic signaling by reversing stress-induced downregulation of AMPA receptor subunits (GluA1/GluA2) and restoring synaptic plasticity. In the hippocampus and amygdala, it prevents stress-induced dendritic atrophy, spine loss, and CA3 pyramidal cell damage—likely through opioid receptor activation and downstream HPA axis effects. It increases BDNF levels and promotes neurogenesis. The combination of opioid agonism, glutamate normalization, and neuroplasticity enhancement underlies its unique profile.