Neural Circuit Mechanisms of General Anaesthesia Induction: Current Advances and Future Directions

General anaesthesia is traditionally divided into three distinct stages: induction, maintenance, and recovery. However, much of the existing literature has primarily focused on elucidating the mechanisms involved in the recovery phase, yielding several notable advancements. It is essential to recognize, however, that the induction and recovery phases represent two distinct processes. Studies in the induction phase have mainly centred on the impact of inhalational and intravenous anaesthetics on neural circuits, particularly those in the cortical and subcortical nuclei, as well as their specific effects on various neurotransmitters. Yet, the precise neural circuit mechanisms underlying anaesthetic induction still require further exploration. General anaesthetics influence neural circuitry by targeting neurons in particular nuclei, with their effects varying according to the distinct properties of individual anaesthetic agents. During the induction of anaesthesia, both the cortex and subcortical nuclei are significantly involved, with the inhibition of the subthalamic nucleus considered a core mechanism underlying this process. Notably, the periventricular thalamus, as part of the thalamus structure, holds particular importance in regulating the loss of consciousness. Additionally, the spinal cord and peripheral nervous system may play a potentially important role during the induction phase of general anaesthesia. Gaining a deeper understanding of the mechanisms underlying anaesthetic induction could reveal potential neuroanatomical targets that elucidate the alterations in consciousness during this phase of general anaesthesia. Such insights are invaluable in the quest for more effective, precise, and controllable anaesthetic practices, thereby enhancing the selection and combination of anaesthetic agents.