Endocannabinoid signaling in hypothalamic circuits regulates arousal from general anesthesia in mice
Haixing Zhong, … , Lize Xiong, Xia Zhang
Haixing Zhong, … , Lize Xiong, Xia Zhang
Published May 2, 2017
Citation Information: J Clin Invest. 2017;127(6):2295-2309. https://doi.org/10.1172/JCI91038.
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Research Article Neuroscience

Endocannabinoid signaling in hypothalamic circuits regulates arousal from general anesthesia in mice

Abstract

Consciousness can be defined by two major attributes: awareness of environment and self, and arousal, which reflects the level of awareness. The return of arousal after general anesthesia presents an experimental tool for probing the neural mechanisms that control consciousness. Here we have identified that systemic or intracerebral injection of the cannabinoid CB1 receptor (CB1R) antagonist AM281 into the dorsomedial nucleus of the hypothalamus (DMH) — but not the adjacent perifornical area (Pef) or the ventrolateral preoptic nucleus of the hypothalamus (VLPO) — accelerates arousal in mice recovering from general anesthesia. Anesthetics selectively activated endocannabinoid (eCB) signaling at DMH glutamatergic but not GABAergic synapses, leading to suppression of both glutamatergic DMH-Pef and GABAergic DMH-VLPO projections. Deletion of CB1R from widespread cerebral cortical or prefrontal cortical (PFC) glutamatergic neurons, including those innervating the DMH, mimicked the arousal-accelerating effects of AM281. In contrast, CB1R deletion from brain GABAergic neurons or hypothalamic glutamatergic neurons did not affect recovery time from anesthesia. Inactivation of PFC-DMH, DMH-VLPO, or DMH-Pef projections blocked AM281-accelerated arousal, whereas activation of these projections mimicked the effects of AM281. We propose that decreased eCB signaling at glutamatergic terminals of the PFC-DMH projection accelerates arousal from general anesthesia through enhancement of the excitatory DMH-Pef projection, the inhibitory DMH-VLPO projection, or both.

Authors

Haixing Zhong, Li Tong, Ning Gu, Fang Gao, Yacheng Lu, Rou-gang Xie, Jingjing Liu, Xin Li, Richard Bergeron, Lisa E. Pomeranz, Ken Mackie, Feng Wang, Chun-Xia Luo, Yan Ren, Sheng-Xi Wu, Zhongcong Xie, Lin Xu, Jinlian Li, Hailong Dong, Lize Xiong, Xia Zhang

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Figure 2

Electrophysiological and ultrastructural characteristics of DMH GABAergic and glutamatergic neurons.

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Electrophysiological and ultrastructural characteristics of DMH GABAergi...
(A) Sample current clamp traces (>20 repetitions) show two distinct types of DMH neurons with or without low-threshold spikes, i.e., LTS+ or LTS–, respectively, elicited when the membrane is depolarized from negative potentials. (B) Sample current clamp traces (>20 repetitions) of LTS+ or LTS– (top) were recorded from fluorescent DMH neurons (bottom photos) of GABAergic (GABA) and glutamatergic neurons (Glutamate) from GAD67-GFP and vGLUT2-iCreERT2 mutant mice, respectively. (C–F) Electron microscopic images (3 mice) show CB1R-immunoreactive peroxidase reaction product in DMH GABAergic axonal terminals (iT in C and D) or glutamatergic axonal terminals (eT in E and F). Black arrowheads identify symmetric and asymmetric synaptic contacts of presumed GABAergic and glutamatergic nature, respectively, with the neuronal soma profile (Soma) or dendritic profile (D). Scale bars: 0.25 μm.