Relationship between general anesthesia and memory in Drosophila involving the cAMP/PKA pathways and adhesion-related molecules.

On undergoing an operation under general anesthesia, we tend to lose consciousness, and on recovering from the anesthetic effect, we realize a memory loss during the operation, but do remember the happenings before the operation. It implies that the anesthesia deprivers us of short-term memory without affecting long-term memory. Drosophila melanogaster is known to be an excellent model for genetic studies related to general anesthesia and memory. The various mutants in the genes related to general anesthesia and memory have been found to influence these mechanisms at the molecular level. In Drosophila, learning and memory are classified into four distinct phases: (1) short-term memory (STM), (2) middle-term memory (MTM), (3) longer-lasting anesthesia-resistant memory (ARM), and (4) long-term memory (LTM). On the other hand, based on the genetic studies of the putative target molecules of general anesthetics in model animals, the anesthetic action is classified into five pathways: (1) presynaptic pathway including action potential production, its transmission, and neurotransmitter release; (2) postsynaptic pathway including inhibitory receptors for sleep and pain; (3) memory pathway coupled with cAMP/PKA signaling; (4) adhesion pathway in neuron; and (5) energy production pathway. Memory and adhesion pathways of the anesthetic action are developed in the Drosophila melanogaster model. Many mutants of general anesthesia and those of memory are overlapped suggesting that common molecules and signal pathways are involved in both phenomena. In this review, we will describe the relation between anesthesia and memory, especially highlighting the interaction between the general anesthetics and STM and MTM processes in Drosophila, especially concentrating on the cAMP/PKA signaling and molecular adhesion pathways.