To increase basal rate of NLG1 cleavage, cultures were incubated with bicuculline (50 μM) and 4AP (25 μM) 2 days prior to imaging (Figures 3A and 3B). Interestingly, terminals apposing synapses with GFP-NLG1-ΔSD3 exhibited faster FM4-64 unloading kinetics (τ = 46.1 ± 1.2 s; Figure 6G) than terminals contacting GFP-NLG1-expressing cells (τ = 60.5 ± 1.5 s), indicating that blocking NLG1 cleavage increases presynaptic

release probability. To address whether cleavage of NLG1 is regulated by activity in vivo, we measured NLG1-NTFs generated during MK 1775 pilocarpine-induced status epilepticus (PSE) in mice. Intraperitoneal administration of pilocarpine in P60 mice induced robust seizures and resulted in a 2.2 ± 0.3-fold increase of soluble NLG1-NTFs in the hippocampus after 2 hr PSE (Figures 7A–7C). To test whether MMP9 is involved in PSE-induced NLG1 cleavage, we performed pilocarpine injections in MMP9 KO mice. Notably, 2 hr

PSE characterized by robust behavioral seizures failed to elevate soluble NLG1-NTFs in MMP9 KO hippocampus (1.1 ± 0.1 relatively to control; Selleckchem FRAX597 Figures 7B and 7C). As a control for epileptic activity, both WT and MMP9 KO mice exhibited upregulation of the activity-regulated protein Arc/Arg3.1 after PSE (Figure 7B). Given the enrichment of NLG1-NTFs during the first postnatal weeks (Figures 2G and 2H), we addressed whether NLG1 cleavage is regulated by sensory experience during development. For this, we subjected mice to 5 days of dark rearing (DR) from P21–P26, a period of heightened sensory-evoked refinement of visual cortical circuits (Hensch, 2004), and subsequently re-exposed them to light for a brief period of 2 hr (DR+2hL, Figure 7D). This protocol induces rapid synaptic remodeling in the visual cortex and results alsactide in extensive molecular, functional, and structural synaptic changes (Philpot et al., 2001; Tropea et al., 2010). With this paradigm, 2 hr of re-exposure to light after 5 days of DR caused an increase in NLG1

cleavage in the visual cortex of WT mice (DR: 1.0 ± 0.1; DR+2hL: 1.5 ± 0.2, relatively to light-reared (LR) group; Figures 7E and 7F), but not in MMP9 KO animals (DR: 0.9 ± 0.1; DR+2hL: 1.0 ± 0.1; relative to LR group). Together these findings indicate that increased neuronal activity in vivo triggers MMP9-dependent cleavage of NLG1 in both mature and developing circuits. Although implicated in diverse forms of activity-dependent synaptic maturation and plasticity (Choi et al., 2011; Chubykin et al., 2007; Jung et al., 2010), it has been unclear whether neuroligins acutely regulate synapse function and whether the neuroligin-neurexin transsynaptic complex undergoes dynamic dissociation. Here we have shown that increased neuronal activity decreases synaptic NLG1 in minutes.