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Selectively driving cholinergic fibers optically in the thalamic reticular nucleus promotes sleep.

Ni KM, Hou XJ, Yang CH, Dong P, Li Y, Zhang Y, Jiang P, Berg DK, Duan S, Li XM - Elife (2016)

Bottom Line: It does not affect REM sleep.These findings stand in sharp contrast to previous reports of cholinergic activity driving arousal.Our results provide new insight into the mechanisms controlling sleep.

View Article: PubMed Central - PubMed

Affiliation: Department of Neurobiology, Institute of Neuroscience, Key Laboratory of Medical Neurobiology of the Ministry of Health of China, Collaborative Innovation Center for Brain Science, Zhejiang University School of Medicine, Hangzhou, China.

ABSTRACT
Cholinergic projections from the basal forebrain and brainstem are thought to play important roles in rapid eye movement (REM) sleep and arousal. Using transgenic mice in which channelrhdopsin-2 is selectively expressed in cholinergic neurons, we show that optical stimulation of cholinergic inputs to the thalamic reticular nucleus (TRN) activates local GABAergic neurons to promote sleep and protect non-rapid eye movement (NREM) sleep. It does not affect REM sleep. Instead, direct activation of cholinergic input to the TRN shortens the time to sleep onset and generates spindle oscillations that correlate with NREM sleep. It does so by evoking excitatory postsynaptic currents via α7-containing nicotinic acetylcholine receptors and inducing bursts of action potentials in local GABAergic neurons. These findings stand in sharp contrast to previous reports of cholinergic activity driving arousal. Our results provide new insight into the mechanisms controlling sleep.

No MeSH data available.


Related in: MedlinePlus

Direct stimulation of GABAergic neurons in the TRN promoted sleep onset and altered sleep architecture.(A) Direct optical drive (10-ms pulses, lower) induced bursts of APs in GABAergic neurons (upper). (B) Representative spindle oscillations evoked by different optical stimulation paradigms (1, 8, or 20 Hz). (C) Probability of spindle waves induced by 1 Hz, 8 Hz, and 20 Hz. (D) Stimulation protocol in the TRN of VGAT-ChR2 mice. A 473 nm laser (1.5 mW) was given at 8 Hz for 1 s at 6-s intervals for 1 hr. (E) Sleep onset time of VGAT-ChR2-Sti and VGAT-ChR2-NonSti mice. (F) Total sleep time evoked by direct optical stimulation of GABAergic neurons in the TRN of VGAT-ChR2 mice and unstimulated controls. (G) Durations of time in waking, NREM, and REM states for VGAT-ChR2 mice with and without direct optical stimulation of GABAergic neurons in the TRN. Stimulation substantially decreased the duration of wake time, while increasing the duration of NREM time; it had no effect on REM time. In (C, E, F, G), data represent mean ± SEM (n = 7 mice, *p < 0.05, **p < 0.01, two-tailed t-test between VGAT-ChR2 mice with spindle-like stimulation and VGAT-ChR2 mice without stimulation).DOI:http://dx.doi.org/10.7554/eLife.10382.012
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fig7: Direct stimulation of GABAergic neurons in the TRN promoted sleep onset and altered sleep architecture.(A) Direct optical drive (10-ms pulses, lower) induced bursts of APs in GABAergic neurons (upper). (B) Representative spindle oscillations evoked by different optical stimulation paradigms (1, 8, or 20 Hz). (C) Probability of spindle waves induced by 1 Hz, 8 Hz, and 20 Hz. (D) Stimulation protocol in the TRN of VGAT-ChR2 mice. A 473 nm laser (1.5 mW) was given at 8 Hz for 1 s at 6-s intervals for 1 hr. (E) Sleep onset time of VGAT-ChR2-Sti and VGAT-ChR2-NonSti mice. (F) Total sleep time evoked by direct optical stimulation of GABAergic neurons in the TRN of VGAT-ChR2 mice and unstimulated controls. (G) Durations of time in waking, NREM, and REM states for VGAT-ChR2 mice with and without direct optical stimulation of GABAergic neurons in the TRN. Stimulation substantially decreased the duration of wake time, while increasing the duration of NREM time; it had no effect on REM time. In (C, E, F, G), data represent mean ± SEM (n = 7 mice, *p < 0.05, **p < 0.01, two-tailed t-test between VGAT-ChR2 mice with spindle-like stimulation and VGAT-ChR2 mice without stimulation).DOI:http://dx.doi.org/10.7554/eLife.10382.012

Mentions: Having found that cholinergic input to PV-containing TRN neurons generates spindle oscillations and promotes NREM sleep via α7-nAChRs, we wanted to confirm whether direct stimulation of TRN GABAergic neurons could achieve the same effects. For this purpose, we used VGAT-ChR2 mice in which ChR2 was specifically expressed in the GABAergic neurons (Zhao et al., 2011) so that those neurons would be selectively activated by light pulses delivered to the TRN. Testing the paradigm first in vitro showed that a light pulse of 10 ms applied to an acute slice could induce bursts of APs in GABAergic neurons of the TRN (Figure 7A). Testing three different optical stimulation patterns in vivo (20 Hz, 8 Hz, or single 10 ms pulses) indicated that 8 Hz stimulation was most successful at evoking spindle oscillations both in waking and NREM states (P < 0.05, Figure 7B,C). Accordingly, we used that stimulation protocol (10 ms of 8 Hz for 1 s at 6-s intervals) to induce sleep in VGAT-ChR2 mice, which were raised under a 12-hr light/12-hr dark cycle (Figure 7D). Blue laser light of 473 nm was delivered into the TRN through a 200 μm optical fiber for 1 hr starting 4 hr after 'light off'. Both EEG and EMG were recorded, and sleep onset and sleep architecture were then measured. Optical stimulation significantly reduced the sleep onset time of VGAT-ChR2 mice (VGAT-ChR2-Sti, 27.2 ± 3.2 min) compared with that of the controls (VGAT-ChR2-NonSti; 5.5 ± 0.8 min, P < 0.01, Figure 7E). Similarly, the duration of sleep during the 1 hr optical stimulation period also increased by 156% compared with that of the controls (P < 0.01, Figure 7F). Furthermore, the architecture of sleep differed greatly in VGAT-ChR2-Sti mice vs. VGAT-ChR2-NonSti mice. Time spent in the NREM phase was significantly greater for VGAT-ChR2-Sti mice (27.2 ± 2.1 min) than for VGAT-ChR2-NonSti mice (15.2 ± 1.3 min, p < 0.01), while no significant differences were seen in the duration of the REM stage (Figure 7G). These results support that elevating the activity of GABAergic neurons in the TRN can promote sleep in ways that mimic the effects of cholinergic excitation of the TRN.10.7554/eLife.10382.012Figure 7.Direct stimulation of GABAergic neurons in the TRN promoted sleep onset and altered sleep architecture.


Selectively driving cholinergic fibers optically in the thalamic reticular nucleus promotes sleep.

Ni KM, Hou XJ, Yang CH, Dong P, Li Y, Zhang Y, Jiang P, Berg DK, Duan S, Li XM - Elife (2016)

Direct stimulation of GABAergic neurons in the TRN promoted sleep onset and altered sleep architecture.(A) Direct optical drive (10-ms pulses, lower) induced bursts of APs in GABAergic neurons (upper). (B) Representative spindle oscillations evoked by different optical stimulation paradigms (1, 8, or 20 Hz). (C) Probability of spindle waves induced by 1 Hz, 8 Hz, and 20 Hz. (D) Stimulation protocol in the TRN of VGAT-ChR2 mice. A 473 nm laser (1.5 mW) was given at 8 Hz for 1 s at 6-s intervals for 1 hr. (E) Sleep onset time of VGAT-ChR2-Sti and VGAT-ChR2-NonSti mice. (F) Total sleep time evoked by direct optical stimulation of GABAergic neurons in the TRN of VGAT-ChR2 mice and unstimulated controls. (G) Durations of time in waking, NREM, and REM states for VGAT-ChR2 mice with and without direct optical stimulation of GABAergic neurons in the TRN. Stimulation substantially decreased the duration of wake time, while increasing the duration of NREM time; it had no effect on REM time. In (C, E, F, G), data represent mean ± SEM (n = 7 mice, *p < 0.05, **p < 0.01, two-tailed t-test between VGAT-ChR2 mice with spindle-like stimulation and VGAT-ChR2 mice without stimulation).DOI:http://dx.doi.org/10.7554/eLife.10382.012
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fig7: Direct stimulation of GABAergic neurons in the TRN promoted sleep onset and altered sleep architecture.(A) Direct optical drive (10-ms pulses, lower) induced bursts of APs in GABAergic neurons (upper). (B) Representative spindle oscillations evoked by different optical stimulation paradigms (1, 8, or 20 Hz). (C) Probability of spindle waves induced by 1 Hz, 8 Hz, and 20 Hz. (D) Stimulation protocol in the TRN of VGAT-ChR2 mice. A 473 nm laser (1.5 mW) was given at 8 Hz for 1 s at 6-s intervals for 1 hr. (E) Sleep onset time of VGAT-ChR2-Sti and VGAT-ChR2-NonSti mice. (F) Total sleep time evoked by direct optical stimulation of GABAergic neurons in the TRN of VGAT-ChR2 mice and unstimulated controls. (G) Durations of time in waking, NREM, and REM states for VGAT-ChR2 mice with and without direct optical stimulation of GABAergic neurons in the TRN. Stimulation substantially decreased the duration of wake time, while increasing the duration of NREM time; it had no effect on REM time. In (C, E, F, G), data represent mean ± SEM (n = 7 mice, *p < 0.05, **p < 0.01, two-tailed t-test between VGAT-ChR2 mice with spindle-like stimulation and VGAT-ChR2 mice without stimulation).DOI:http://dx.doi.org/10.7554/eLife.10382.012
Mentions: Having found that cholinergic input to PV-containing TRN neurons generates spindle oscillations and promotes NREM sleep via α7-nAChRs, we wanted to confirm whether direct stimulation of TRN GABAergic neurons could achieve the same effects. For this purpose, we used VGAT-ChR2 mice in which ChR2 was specifically expressed in the GABAergic neurons (Zhao et al., 2011) so that those neurons would be selectively activated by light pulses delivered to the TRN. Testing the paradigm first in vitro showed that a light pulse of 10 ms applied to an acute slice could induce bursts of APs in GABAergic neurons of the TRN (Figure 7A). Testing three different optical stimulation patterns in vivo (20 Hz, 8 Hz, or single 10 ms pulses) indicated that 8 Hz stimulation was most successful at evoking spindle oscillations both in waking and NREM states (P < 0.05, Figure 7B,C). Accordingly, we used that stimulation protocol (10 ms of 8 Hz for 1 s at 6-s intervals) to induce sleep in VGAT-ChR2 mice, which were raised under a 12-hr light/12-hr dark cycle (Figure 7D). Blue laser light of 473 nm was delivered into the TRN through a 200 μm optical fiber for 1 hr starting 4 hr after 'light off'. Both EEG and EMG were recorded, and sleep onset and sleep architecture were then measured. Optical stimulation significantly reduced the sleep onset time of VGAT-ChR2 mice (VGAT-ChR2-Sti, 27.2 ± 3.2 min) compared with that of the controls (VGAT-ChR2-NonSti; 5.5 ± 0.8 min, P < 0.01, Figure 7E). Similarly, the duration of sleep during the 1 hr optical stimulation period also increased by 156% compared with that of the controls (P < 0.01, Figure 7F). Furthermore, the architecture of sleep differed greatly in VGAT-ChR2-Sti mice vs. VGAT-ChR2-NonSti mice. Time spent in the NREM phase was significantly greater for VGAT-ChR2-Sti mice (27.2 ± 2.1 min) than for VGAT-ChR2-NonSti mice (15.2 ± 1.3 min, p < 0.01), while no significant differences were seen in the duration of the REM stage (Figure 7G). These results support that elevating the activity of GABAergic neurons in the TRN can promote sleep in ways that mimic the effects of cholinergic excitation of the TRN.10.7554/eLife.10382.012Figure 7.Direct stimulation of GABAergic neurons in the TRN promoted sleep onset and altered sleep architecture.

Bottom Line: It does not affect REM sleep.These findings stand in sharp contrast to previous reports of cholinergic activity driving arousal.Our results provide new insight into the mechanisms controlling sleep.

View Article: PubMed Central - PubMed

Affiliation: Department of Neurobiology, Institute of Neuroscience, Key Laboratory of Medical Neurobiology of the Ministry of Health of China, Collaborative Innovation Center for Brain Science, Zhejiang University School of Medicine, Hangzhou, China.

ABSTRACT
Cholinergic projections from the basal forebrain and brainstem are thought to play important roles in rapid eye movement (REM) sleep and arousal. Using transgenic mice in which channelrhdopsin-2 is selectively expressed in cholinergic neurons, we show that optical stimulation of cholinergic inputs to the thalamic reticular nucleus (TRN) activates local GABAergic neurons to promote sleep and protect non-rapid eye movement (NREM) sleep. It does not affect REM sleep. Instead, direct activation of cholinergic input to the TRN shortens the time to sleep onset and generates spindle oscillations that correlate with NREM sleep. It does so by evoking excitatory postsynaptic currents via α7-containing nicotinic acetylcholine receptors and inducing bursts of action potentials in local GABAergic neurons. These findings stand in sharp contrast to previous reports of cholinergic activity driving arousal. Our results provide new insight into the mechanisms controlling sleep.

No MeSH data available.


Related in: MedlinePlus