Intermale aggression is used to establish social rank. Several neuronal populations have been implicated in aggression, but the circuit mechanisms that shape this innate behavior and coordinate its different components (including attack execution and reward) remain elusive. We show that dopamine transporter-expressing neurons in the hypothalamic ventral premammillary nucleus (PMv neurons) organize goal-oriented aggression in male mice. Activation of PMv neurons triggers attack behavior; silencing these neurons interrupts attacks. Regenerative PMv membrane conductances interacting with recurrent and reciprocal excitation explain how a brief trigger can elicit a long-lasting response (hysteresis). PMv projections to the ventrolateral part of the ventromedial hypothalamic and the supramammillary nuclei control attack execution and aggression reward, respectively. Brief manipulation of PMv activity switched the dominance relationship between males, an effect persisting for weeks. These results identify a network structure anchored in PMv neurons that organizes aggressive behavior and, as a consequence, determines intermale hierarchy.

Alcohol intoxication at early ages is a risk factor for the development of addictive behavior. To uncover neuronal molecular correlates of acute ethanol intoxication, we used stable-isotope–labeled mice combined with quantitative mass spectrometry to screen more than 2,000 hippocampal proteins, of which 72 changed synaptic abundance up to twofold after ethanol exposure. Among those were mitochondrial proteins and proteins important for neuronal morphology, including MAP6 and ankyrin-G. Based on these candidate proteins, we found acute and lasting molecular, cellular, and behavioral changes following a single intoxication in alcohol-naïve mice. Immunofluorescence analysis revealed a shortening of axon initial segments. Longitudinal two-photon in vivo imaging showed increased synaptic dynamics and mitochondrial trafficking in axons. Knockdown of mitochondrial trafficking in dopaminergic neurons abolished conditioned alcohol preference in Drosophila flies. This study introduces mitochondrial trafficking as a process implicated in reward learning and highlights the potential of high-resolution proteomics to identify cellular mechanisms relevant for addictive behavior.

The current standard of care for moderate to severe ischemic stroke is thrombolytic therapy with tissue plasminogen activator (tPA). Treatment with tPA can significantly improve neurological outcomes; however, thrombolytic therapy is associated with an increased risk of intracerebral hemorrhage (ICH). The risk of hemorrhage significantly limits the use of thrombolytic therapy and identifying pathways induced by tPA that increase this risk could provide new therapeutic options to extend thrombolytic therapy to a wider patient population. Here, we investigate the role of protein kinase (PK)Cβ phosphorylation of the tight junction protein occludin during ischemic stroke and its role in cerebrovascular permeability. We demonstrate that activation of this pathway by tPA is associated with an increased risk of ICH. Middle cerebral artery occlusion (MCAO) increased occludin serine 490 (S490) phosphorylation in the ischemic penumbra in a tPA-dependent manner, as tPA-/- mice were significantly protected from MCAO-induced occludin phosphorylation. Intra-ventricular injection of tPA in the absence of ischemia was sufficient to induce occludin phosphorylation and vascular permeability in a PKCb-dependent manner. Blocking occludin phosphorylation either by targeted expression of a non-phosphorylatable form of occludin (S490A) or by pharmacologic inhibition of PKCβ, reduced MCAO-induced permeability and improved functional outcome. Further, inhibiting PKCβ after MCAO prevented ICH associated with delayed thrombolysis. These results reveal that PKCβ phosphorylation of occludin is a downstream mediator of tPA-induced cerebrovascular permeability and suggest that PKCb inhibitors could improve stroke outcome and prevent ICH associated with delayed thrombolysis, potentially extending the window for thrombolytic therapy in stroke.