Memory impairment induced by cholinergic antagonists injected into the mushroom bodies of the honeybee.

The role of honeybee central brain structures, suspected to be cholinergic, has been studied in learning and memory. The nicotinic antagonist mecamylamine and the muscarinic antagonist scopolamine were locally injected into the calyces and the alpha-lobes of mushroom bodies, and their effects on memory acquisition and retrieval were investigated using one-trial olfactory conditioning of the proboscis extension reflex. A strong impairment of the olfactory learning was noticed following mecamylamine injection into the mushroom body calyces. Mecamylamine and scopolamine disturbed retrieval processes when injected into the alpha-lobes of mushroom bodies but remain without effect on these processes when injected into the mushroom body calyces. These results emphasise the role of the cholinergic networks of the mushroom bodies in the formation and recall of memory in the honeybee. They suggest that the role of the brain structures in these processes is sequential. Mushroom body calyces involved in the associative process of olfactory learning could be relayed by the alpha-lobes for information retrieval.