Physiological and behavioral pharmacology of ethanol in honey bees

Ethanol has been consumed by humans since the dawn of civilization and, over the course of millennia, a wide variety of ethanol-rich drinks have been produced across cultures. Traditionally, it was believed that only humans voluntarily consume ethanol and become inebriated by it. However, a growing amount of evidence is showing that several non-human animal species spontaneously consume ethanol in nature. Among these, there is the honey bee (Apis mellifera), which can find ethanol in decaying fruits and in the fermented nectar of flowers. Importantly, honey bees represent a useful animal model of ethanol consumption as, like humans, they voluntarily consume ethanol, they show acute dose-dependent motor and postural signs of inebriation, they display ethanol-induced disruption of cognitive functions and social behavior, and they develop ethanol dependence. Moreover, they are small, easy to acquire and easy to maintain in the laboratory. Finally, we possess a vast database of information on their natural history, physiology, genetics and behavior, with their ethogram comprising a wide variety of basic to complex behaviors, including the capacity to self-administer large quantities of ethanol. The present article reviews what is currently known about the physiological and behavioral pharmacology of ethanol in honey bees. The topics covered include the effect of ethanol on gene expression, epigenetic changes of DNA, neuronal stress, posture, locomotion, learning (comprising classical and operant conditioning), communication, social feeding (trophallaxis), aggression and foraging-related decision-making in honey bees.