Effects of ethanol exposure and withdrawal on olfactory sensitivity and learning and memory in honeybees(Apis mellifera)

Abstract

Alcohol abuse poses a global health concern. This study examines how alcohol exposure and withdrawal affect honeybees’ (Apis mellifera) learning, memory, and olfactory sensitivity areas still largely unknown. It provides scientific evidence to understand behavioral changes from alcohol and withdrawal. The study consisted of two experiments: (1) Acute ethanol exposure: honeybees were fed with sucrose solutions containing 5 %, 10 %, 20 %, and 30 % ethanol for 72 h; (2) Alcohol withdrawal experiment: The continuous exposure group was fed a 10 % ethanol solution for 10 days. The withdrawal group received ethanol for the first 5 days, then switched to a 50 % sucrose solution for the remaining 5 days. The control group was fed a 50 % sucrose solution all along. Daily mortality was recorded for all groups. On day 10, sucrose sensitivity and learning and memory abilities (via the proboscis extension response, PER) were tested. Our results demonstrated that Ethanol decreases honeybee survival in a dose − and time − dependent manner, and withdrawal increases mortality. Both continuous exposure and withdrawal seriously undermine honeybees’ learning and long − term memory, implying ethanol − induced cognitive damage is irreversible. Gene expression analysis shows that in the withdrawal group, Mrjp1, CREB, Obp16, and Dop3 genes linked to bees’ neural activity have lower expression levels than the control group. Mrjp1 and CREB expression are also lower than in the continuous exposure group. This study offers new evidence into alcohol’s effects on insect nervous systems, and provides insights into related disorders in human health.