Activating an anterior nucleus gigantocellularis subpopulation triggers emergence from pharmacologically-induced coma in rodents

Abstract

Multiple areas within the reticular activating system (RAS) can hasten awakening from sleep or light planes of anesthesia. However, stimulation in individual sites has shown limited recovery from deep global suppression of brain activity, such as coma. Here we identify a subset of RAS neurons within the anterior portion of nucleus gigantocellularis (aNGC) capable of producing a high degree of awakening represented by a broad high frequency cortical reactivation associated with organized movements and behavioral reactivity to the environment from two different models of deep pharmacologically-induced coma (PIC): isoflurane (1.25%–1.5%) and induced hypoglycemic coma. Activating aNGC neurons triggered awakening by recruiting cholinergic, noradrenergic, and glutamatergic arousal pathways. In summary, we identify an evolutionarily conserved population of RAS neurons, which broadly restore cerebral cortical activation and motor behavior in rodents through the coordinated activation of multiple arousal-promoting circuits.

Continuous regimens of cortico-motor integration calibrate levels of arousal during emergence from anesthesia

“…The skull was fixed to the stereotaxic frame. The wound edge was infiltrated with local anesthetic (bupivacaine 0.5%) and a designed-head holder device was placed on the skull to ensure durable head restraint without the need for ear bars as in Gao et al 18 . Two small craniotomies were made to target motor cortex (AP: 1.5-2 mm ML:1.2mm DV:0.2 mm).…”

“…Bicuculline methiodide (Tocris) was dissolved in 0.9% saline in a stock concentration of 20 mM and then diluted to yield a final concentration of 10 mM. 200 nl of drug were injected in mice (n=3) using a microinjector (Micro 4, WPI) via Hamilton syringe connected to a cannula using tygon tubing at a rate of 200 nl/15s as we previously described in Gao and colleagues 18 .…”

“…We previously published a model of arousal in which we awaken animals via the anterior portion of the nucleus gigantocellularis (aNGC) from a low brain activity state(constant exposure to isoflurane 1.3%) 18 . To assess the level of arousal reached by this animal model using the proposed method in this manuscript, we implanted animals(n=3) with a unilateral cannula to acutely microinject bicuculline in aNGC.…”

“…To determine the sample sizes of the experimental groups we performed pilot experiments with 3 mice for the pharmacologic experiments 18 and for those mice exposed to prolonged anesthetic ramps. We considered the strength of the effect and the variance across the groups to determine the sample size (number of units).…”

Neural Signatures of α2 Adrenergic Agonist-Induced Unconsciousness and Awakening by Antagonist

“…256 How the unconscious state can be actively reversed has been investigated in anesthetized subjects 257 and subjects with coma due to other causes with a limited degree of recovery (Alkire et al, 2007; 258 Schiff et al, 2007; Xu et al, 2019). Gao and colleagues recently reported that activating nucleus 259 gigantocellularis neurons in the reticular activating system elicited a high degree of awakening, 260including cortical, autonomic, and behavioral recovery, in both isoflurane anesthetized and 261 hypoglycemia-induced coma rodents(Gao et al, 2019). Activation of dopamine and 262 norepinephrine pathways are also shown to promote behavioral arousal in anesthetized rodents 263 with inhaled anesthetics(Kenny et al, 2015; Taylor et al, 2016).…”