GABAergic Neurons in the Dorsal–Intermediate Lateral Septum Regulate Sleep–Wakefulness and Anesthesia in Mice

Abstract

Background The γ-aminobutyric acid–mediated (GABAergic) inhibitory system in the brain is critical for regulation of sleep–wake and general anesthesia. The lateral septum contains mainly GABAergic neurons, being cytoarchitectonically divided into the dorsal, intermediate, and ventral parts. This study hypothesized that GABAergic neurons of the lateral septum participate in the control of wakefulness and promote recovery from anesthesia. Methods By employing fiber photometry, chemogenetic and optogenetic neuronal manipulations, anterograde tracing, in vivo electrophysiology, and electroencephalogram/electromyography recordings in adult male mice, the authors measured the role of lateral septum GABAergic neurons to the control of sleep–wake transition and anesthesia emergence and the corresponding neuron circuits in arousal and emergence control. Results The GABAergic neurons of the lateral septum exhibited high activities during the awake state by in vivo fiber photometry recordings (awake vs. non–rapid eye movement sleep: 3.3 ± 1.4% vs. –1.3 ± 1.2%, P < 0.001, n = 7 mice/group; awake vs. anesthesia: 2.6 ± 1.2% vs. –1.3 ± 0.8%, P < 0.001, n = 7 mice/group). Using chemogenetic stimulation of lateral septum GABAergic neurons resulted in a 100.5% increase in wakefulness and a 51.2% reduction in non–rapid eye movement sleep. Optogenetic activation of these GABAergic neurons promoted wakefulness from sleep (median [25th, 75th percentiles]: 153.0 [115.9, 179.7] s to 4.0 [3.4, 4.6] s, P = 0.009, n = 5 mice/group) and accelerated emergence from isoflurane anesthesia (514.4 ± 122.2 s vs. 226.5 ± 53.3 s, P < 0.001, n = 8 mice/group). Furthermore, the authors demonstrated that the lateral septum GABAergic neurons send 70.7% (228 of 323 cells) of monosynaptic projections to the ventral tegmental area GABAergic neurons, preferentially inhibiting their activities and thus regulating wakefulness and isoflurane anesthesia depth. Conclusions The results uncover a fundamental role of the lateral septum GABAergic neurons and their circuit in maintaining awake state and promoting general anesthesia emergence time. Editor’s Perspective What We Already Know about This Topic What This Article Tells Us That Is New

Regulation of Neural Circuitry under General Anesthesia: New Methods and Findings

“…The lateral septum contains GABAergic neurons that project to multiple wakefulnesspromoting subregions. The calcium activity of the dorsal-intermediate lateral septal GABAergic neuron changes in both the processes of induction and emergence, similar to the trend observed in the sleep-wake cycle [55]. Collectively, these in vivo calcium imaging findings suggest that multiple brain nuclei and neural circuits known to regulate the sleep-wake cycle play a similar role in general anesthesia (Table 1).…”

“…Chemogenetic activation of these neurons reliably produces slow-wave sleep and facilitates general anesthesia, and chemogenetic inhibition shortens the general anesthesia time and disrupts natural sleep [ 9 ]. Recent studies have found that chemogenetic activation of GABAergic neurons in other brain regions, such as the VTA [ 79 ] and RMTg [ 80 ], promotes an anesthesia state as well, whereas chemogenetic activation of dorsal–intermediate lateral septum GABAergic neurons contributes to anesthesia emergence [ 55 ]. The fact that sleep-promoting GABAergic neurons in the aforementioned regions similarly contribute to anesthetic-state transitions further supports a common regulatory mechanism between the states of sleep and general anesthesia ( Table 1 ).…”

Lateral septum-lateral hypothalamus circuit dysfunction in comorbid pain and anxiety

“…The lateral septum (LS) is implicated as a hub that regulates affective behaviors, such as reward, feeding, anxiety, fear, sociability, and memory [6][7][8]. It is well known that LS neurons are predominantly GABAergic, with only a small population of glutamatergic cells in the most ventral region [9].…”

“…The lateral hypothalamic area (LH) is a vital controller of arousal, feeding, and metabolism, integrating sensory information about the world and the body [8,16]. The LH had been identified as a brain region responsive to pain stimuli and chronic pain-induced maladaptive anxiety that is capable of controlling pain-related behavioral responses by feeding [17,18].…”

Glutamatergic neurons in the paraventricular hypothalamic nucleus regulate isoflurane anesthesia in mice

“…The paraventricular hypothalamic nucleus (PVH), located in the ventral diencephalon adjacent to the third ventricle, has dense mutual projections with structures that modulate sleep–wake behaviors, including the locus coeruleus (LC), 6,7 the parabrachial nucleus (PB), 8,9 the ventrolateral preoptic nucleus (VLPO), PVT, the lateral septum (LS) 10,11 . Previous studies have confirmed that the LC, VLPO, PVT, and LS regulated sleep–wakefulness and anesthesia 3,4,6,9 . The PVH is mostly composed of neuroendocrine neurons, containing corticotropin‐releasing hormone, 12 oxytocin 11 and prodynorphin, 13 in which all the neurons predominantly co‐expressed the mRNA of vesicular glutamate transporter 2 (vglut 2).…”