Summary: Researchers have identified a precise neural pathway that converts emotional stress into immediate wakefulness during non-rapid eye movement (NREM) sleep. In mice, GABAergic neurons in the bed nucleus of the stria terminalis (BNST) rapidly engage glutamatergic neurons in the deep mesencephalic nucleus (DpMe), producing an almost instantaneous arousal. When DpMe glutamatergic neurons were selectively removed, the stress-triggered awakening was greatly diminished, demonstrating this circuit’s essential role. These results clarify how fear and anxiety can swiftly interrupt sleep and suggest new targets for treating stress-related insomnia and mood disorders.
Key Facts:
- Stress pathway: GABAergic neurons in the BNST trigger rapid arousal by activating glutamatergic neurons in the DpMe.
- Essential nodes: Ablation of glutamatergic DpMe neurons markedly reduces stress-induced wakefulness, confirming their crucial role.
- Therapeutic potential: This BNST–DpMe circuit is a promising target for interventions aimed at stress-related sleep disturbances and certain mood disorders.
Background: Emotional states such as fear and anxiety strongly influence sleep–wake regulation. Brain regions within and connected to the amygdala have long been implicated in arousal control, but the specific downstream pathways that convert emotional signals into behavioral wakefulness remained unclear. This study focused on the interaction between inhibitory GABAergic neurons in the BNST and excitatory glutamatergic neurons in the DpMe to explain how emotionally salient stimuli can rapidly terminate NREM sleep.
Using a combination of optogenetics, fiber photometry, targeted neural ablation, and neural tracing in male mice, the researchers mapped and tested the BNST→DpMe circuit. Optogenetic activation of GABAergic BNST terminals within the DpMe during NREM sleep produced an immediate transition to wakefulness and a strong rise in activity of glutamatergic DpMe neurons. Exposure to an aversive air-puff produced similar activation of these DpMe glutamatergic neurons, indicating the circuit responds to emotionally salient stimuli as well as experimental stimulation.
Crucially, selective removal of glutamatergic neurons in the DpMe greatly weakened the arousal response to BNST stimulation, demonstrating that GLUT-DpMe neurons are required to convey the wake-promoting signal. Anatomical tracing showed local inputs to GLUT-DpMe cells but few inhibitory Vgat-positive interneurons among them, suggesting that BNST GABAergic neurons may influence DpMe glutamatergic cells via noncanonical GABAergic mechanisms or more complex local circuitry rather than a simple disinhibition pathway.
Key Questions Answered:
A: Emotional stress activates a direct BNST-to-DpMe circuit that rapidly shifts NREM sleep into wakefulness by engaging glutamatergic neurons in the midbrain.
A: Glutamatergic neurons within the deep mesencephalic nucleus are essential for transmitting the wake-up signal produced by BNST activation.
A: The study identifies a concrete neural pathway that can be overactive in stress-related sleep disruption, offering a specific target for developing therapies to reduce sleep fragmentation caused by anxiety or fear.
Editorial Notes:
- This article was edited by a Neuroscience News editor.
- The journal article was reviewed in full for accuracy.
- Additional context and editorial framing were provided by staff to clarify translational implications.
About this stress and sleep research news
Author: YAMASHINA Naoko
Source: University of Tsukuba
Contact: YAMASHINA Naoko – University of Tsukuba
Image: The image is credited to Neuroscience News
Original Research: Closed access. “The bed nucleus of the stria terminalis–deep mesencephalic nucleus circuit linking emotion and wakefulness” by SAKURAI, Takeshi et al., Journal of Neuroscience.
Abstract
The bed nucleus of the stria terminalis–deep mesencephalic nucleus circuit linking emotion and wakefulness
The bed nucleus of the stria terminalis (BNST), a component of the extended amygdala, integrates emotional and arousal-related information and influences sleep–wake transitions. Prior work has implicated BNST GABAergic neurons in promoting transitions from NREM sleep to wakefulness, but the downstream pathways mediating this effect were not fully defined.
This study identifies a midbrain circuit in which GABAergic BNST neurons promote rapid arousal through projections to the deep mesencephalic nucleus (DpMe), located within the mesencephalic reticular formation. In male mice, optogenetic stimulation of BNST terminals in the DpMe during NREM sleep precipitated immediate wakefulness and increased activity of glutamatergic DpMe neurons, measured by c-fos mRNA expression and calcium imaging. Aversive sensory stimulation (air-puff) similarly engaged these glutamatergic DpMe neurons, indicating that emotionally salient stimuli recruit the same pathway.
Selective ablation of glutamatergic DpMe neurons substantially attenuated arousal responses evoked by BNST stimulation, demonstrating their necessity for signal transmission. Monosynaptic tracing revealed local inputs to glutamatergic DpMe cells, but few Vgat-positive interneurons were identified, implying that BNST GABAergic influences on DpMe glutamatergic neurons may operate through unconventional GABAergic signaling or through more complex local circuits rather than simple disinhibition.
Overall, these results delineate a previously uncharacterized BNST→DpMe circuit that allows emotionally relevant cues to override sleep and trigger wakefulness. By clarifying how stress and fear can rapidly disrupt sleep, this work highlights potential neural targets for developing treatments for stress-related insomnia and other sleep disorders linked to emotional dysregulation.
Funding:
This research was supported by the World Premier International Research Center Initiative (WPI); multiple JSPS KAKENHI grants (including Grant-in-Aid for Scientific Research (B) JP18H02595, Challenging Research (Exploratory) 21K19287, Scientific Research (A) JP21H05036, JP23H04941, and Transformative Research Areas (A) 23H04941); AMED Moonshot Research and Development Program JP21zf0127005; JSPS Fund for the Promotion of Joint International Research 22K213511; and JST CREST JPMJCR24T4.