Characterization of the 5-HT1A receptor of the honeybee (Apis mellifera) and involvement of serotonin in phototactic behavior

Serotonin plays a key role in modulating various physiological and behavioral processes in both protostomes and deuterostomes. The vast majority of serotonin receptors belong to the superfamily of G-protein-coupled receptors. We report the cloning of a cDNA from the honeybee (Am5-ht1A) sharing high similarity with members of the 5-HT₁ receptor class. Activation of Am5-HT_1A by serotonin inhibited the production of cAMP in a dose-dependent manner (EC₅₀ = 16.9 nM). Am5-HT_1A was highly expressed in brain regions known to be involved in visual information processing. Using in vivo pharmacology, we could demonstrate that Am5-HT_1A receptor ligands had a strong impact on the phototactic behavior of individual bees. The data presented here mark the first comprehensive study—from gene to behavior—of a 5-HT_1A receptor in the honeybee, paving the way for the eventual elucidation of additional roles of this receptor subtype in the physiology and behavior of this social insect.