We screened for novel circuits in the mouse brain that promote wakefulness. Chemogenetic activation experiments and electroencephalogram recordings pointed to glutamatergic/nitrergic (NOS1) and GABAergic neurons in the ventral tegmental area (VTA). Activating glutamatergic/NOS1 neurons, which were wake- and rapid eye movement (REM) sleep-active, produced wakefulness through projections to the nucleus accumbens and the lateral hypothalamus. Lesioning the glutamate cells impaired the consolidation of wakefulness. By contrast, activation of GABAergic VTA neurons elicited long-lasting non-rapid-eye-movement-like sleep resembling sedation. Lesioning these neurons produced an increase in wakefulness that persisted for at least 4 months. Surprisingly, these VTA GABAergic neurons were wake- and REM sleep-active. We suggest that GABAergic VTA neurons may limit wakefulness by inhibiting the arousal-promoting VTA glutamatergic and/or dopaminergic neurons and through projections to the lateral hypothalamus. Thus, in addition to its contribution to goal- and reward-directed behaviors, the VTA has a role in regulating sleep and wakefulness.

Peripheral nerve injury causes neuropathic pain accompanied by remarkable microgliosis in the spinal cord dorsal horn. However, it is still debated whether infiltrated monocytes contribute to injury-induced expansion of the microglial population. Here, we found that spinal microgliosis predominantly results from local proliferation of resident microglia but not from infiltrating monocytes after spinal nerve transection (SNT) by using two genetic mouse models (CCR2(RFP/+):CX3CR1(GFP/+) and CX3CR1(creER/+):R26(tdTomato/+) mice) as well as specific staining of microglia and macrophages. Pharmacological inhibition of SNT-induced microglial proliferation correlated with attenuated neuropathic pain hypersensitivities. Microglial proliferation is partially controlled by purinergic and fractalkine signaling, as CX3CR1(-/-) and P2Y12(-/-) mice show reduced spinal microglial proliferation and neuropathic pain. These results suggest that local microglial proliferation is the sole source of spinal microgliosis, which represents a potential therapeutic target for neuropathic pain management.

The shortage of donors is a major challenge for transplantation; however, organs from genetically modified pigs can serve as ideal supplements^1,2. Until now, porcine hearts and kidneys have been successively transplanted into humans^3,4,5,6,7. In this study, heterotopic auxiliary transplantation was used to donate a six-gene-edited pig liver to a brain-dead recipient. The graft function, haemodynamics, and immune and inflammatory responses of the recipient were monitored over the subsequent 10 days. Two hours after portal vein reperfusion of the xenograft, goldish bile was produced, increasing to 66.5 ml by postoperative day 10. Porcine liver-derived albumin also increased after surgery. Alanine aminotransferase levels remained in the normal range, while aspartate aminotransferase levels increased on postoperative day 1 and then rapidly declined. Blood flow velocity in the porcine hepatic artery and portal and hepatic veins remained at an acceptable level. Although platelet numbers decreased early after surgery, they ultimately returned to normal levels. Histological analyses showed that the porcine liver regenerated capably with no signs of rejection. T cell activity was inhibited by anti-thymocyte globulin administration, and B cell activation increased 3 days after surgery and was then inhibited by rituximab. There were no significant peri-operative changes in immunoglobulin G or immunoglobulin M levels. C-reactive protein and procalcitonin levels were initially elevated and then quickly declined. The xenograft remained functional until study completion.

In mice, social defeat stress (SDS), an ethological model for psychosocial stress, induces sleep. Such sleep could enable resilience, but how stress promotes sleep is unclear. Activity-dependent tagging revealed a subset of ventral tegmental area γ-aminobutyric acid (GABA)–somatostatin (VTA ^Vgat-Sst ) cells that sense stress and drive non–rapid eye movement (NREM) and REM sleep through the lateral hypothalamus and also inhibit corticotropin-releasing factor (CRF) release in the paraventricular hypothalamus. Transient stress enhances the activity of VTA ^Vgat-Sst cells for several hours, allowing them to exert their sleep effects persistently. Lesioning of VTA ^Vgat-Sst cells abolished SDS-induced sleep; without it, anxiety and corticosterone concentrations remained increased after stress. Thus, a specific circuit allows animals to restore mental and body functions by sleeping, potentially providing a refined route for treating anxiety disorders.