Figure 1. Discovery of General-Anesthesia-Activated Neurons (AAN) in Hypothalamus.

(A) Left, schematics of interested regions on the brain atlas. A, anterior; P, posterior. Right, representative patterns of Fos⁺ neurons (approximately 0 mm to −1.2 mm from bregma) after 2-hour control (oxygen) versus isoflurane exposure (1~1.2% Isoflurane mixed with oxygen) from n = 4 pairs of mice.

(B-G) Simultaneous in vivo extracellular recording of hypothalamic neurons in the AAN region and the brain states before, during, and after GA. n = 89 neurons across 14 sessions from 7 mice. (B) Schematics of recording chamber and electrode placement. Iso, isoflurane; PFC, prefrontal cortex; EMG, electromyography; Gnd, ground. (C) Representative isoflurane-suppressed (Iso-Sup.) and isoflurane-activated (Iso-Act.) neuron. Top two panels, spike-rate of the example neuron; third, frontal cortex LFP (fLFP); bottom, EMG. Black dashed lines mark the duration of isoflurane exposure. Red dashed lines indicate the period of loss-of-consciousness (LOC). (D) Activity profile of all neurons recorded (n = 89). The spike rate of each neuron was normalized by its peak firing rate. (E-F) Activities of isoflurane-activated neurons (raw spike trains convolved with 1-s Gaussian kernel) aligned with the time when mice lose consciousness (E) or emerge from GA (F). Purple square highlights the neurons that increased firing rate before LOC (E), or decreased firing rate ahead of emergence (F). (G) Categorize the neuronal population based on its response toward isoflurane.

See also Figures S1 and S2