N-methyl serotonin analogues from the Bufo bufo toad venom interact efficiently with the α7 nicotinic acetylcholine receptors

Two low-molecular-weight compounds were isolated from the parotid gland secret of the toad Bufo bufo, which by absorption spectra and HPLC-MS/MS chromatography data correspond to di- and trimethyl derivatives of serotonin (5-hydorxytryptamine): bufotenine (confirmed by counter synthesis) and bufotenidine (5-HTQ). In experiments on competitive radioligand binding, these compounds showed a higher affinity and selectivity for neuronal α7 nicotinic acetylcholine receptors compared with the muscular cholinergic receptors. The most efficient compound in terms of binding value was bufotenine, the efficiency of 5-HTQ was an order of magnitude lower, and the minimal activity was exhibited by serotonin.