Photocontrol of zebrafish behavior with a photoswitchable ligand of nicotinic acetylcholine receptors

The α7 nicotinic acetylcholine receptor (α7 nAChR) is a key modulator of neuronal and immunological signaling, and photopharmacology offers a route to control nicotinic transmission with high spatiotemporal precision. Here we report CPZ-2, a photoswitchable ligand inspired by a patented α7-active scaffold. CPZ-2 shows slow thermal relaxation, high photostability, and reversible photoswitching under one-photon irradiation, together with two-photon-induced photoisomerization monitored directly by HPLC-MS. Radioligand-binding competition performed on the trans-enriched state showed measurable displacement at α7 nAChRs and α1-containing receptors at 10 µM, with lower effects at α3β4 and α4β2 subtypes. Moreover, in wild-type zebrafish larvae, CPZ-2 modulated nicotine-evoked locomotion in a light-dependent manner after bath application. Finally, docking simulations in the α7 orthosteric site support a binding mode compatible with receptor engagement and suggest photostate-dependent differences in the orientation of the distal aromatic group relative to the C-loop region. Together, these data identify CPZ-2 as an uncharged, diffusible photoswitchable nicotinic ligand that combines robust one- and two-photon photochemistry with light-dependent modulation of nicotinic signaling in a wild-type vertebrate model.