Cellular NeuroscienceResearch PaperCannabinoid signaling in inhibitory autaptic hippocampal neurons
Section snippets
Culture preparation
All procedures used in this study were approved by the Animal Care Committees of Indiana University and the University of Washington and conform to the guidelines of the National Institutes of Health on the Care and Use of Animals. Experiments were designed in such a way as to minimize the number of animals used and their suffering. Mouse hippocampal neurons isolated from the CA1–CA3 region were cultured on microislands as described previously (Furshpan et al 1976, Bekkers and Stevens 1991).
Five classes of inhibitory autaptic hippocampal neurons based on their response to stimulation and cannabinoids
IPSCs are easily distinguishable from excitatory postsynaptic currents (EPSCs) by virtue of their visibly slower decay time course (e.g. Fig. 1B, decay time constant for representative EPSC (t½): 4.0 ms; for IPSC: 17.1 ms). Because they represent approximately 10% of the total autaptic population, and are difficult to identify reliably by eye, these neurons were initially avoided/discarded. However in the process of recording from several of these neurons it quickly became apparent that they
Discussion
We have identified four classes of cannabinoid-responsive inhibitory autaptic hippocampal neurons, three of them exhibiting temporally distinct forms of autDSI. As with autDSE, a single autaptic neuron is therefore capable of functionally expressing both the pre- and post-synaptic components of retrograde eCB signaling. This preparation offers an architecturally simple model for detailed investigation of the mechanisms of distinct variants of DSI and how they contrast to those for DSE.
Our
Conclusion
Because they represent less than 10% of cultured hippocampal neurons, and so are encountered too infrequently to yield datasets of sufficient size, inhibitory autaptic hippocampal neurons are generally avoided. The neurons can nonetheless be classified into five populations based on their responses to three stimuli: cannabinoids, a DSI-evoking three second depolarization and a high frequency stimulus. The distinction of such populations among neurons grown under otherwise identical conditions
Acknowledgments
The work was supported by IU LMIC, by NIH grant DA11322 and the Lilly Endowment, Inc.
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2020, Experimental Eye ResearchCitation Excerpt :We tested the ABHD12 blocker DO264 (Ogasawara et al., 2019) find that here too topical application does not result in a reduction in ocular pressure (Fig. 3B: 1 Hr (control): 15.0 ± 0.2, (DO264, 3 mM): 15.5 ± 0.1, n = 7; NS by paired t-test). COX2 actively metabolizes 2-AG in inhibitory neurons (Kim and Alger, 2004; Straiker and Mackie, 2009) and we have shown that COX2 cooperative metabolism with MAGL underlies the more rapid time course of retrograde plasticity in inhibitory neurons (DSI) relative to excitatory neurons (DSE) (Straiker and Mackie, 2009). In principle therefore, a blocker of COX2 might enhance levels of 2-AG, resulting in an inhibition of ocular pressure.
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2019, Trends in Pharmacological SciencesCitation Excerpt :Specifically, these two forms of short-term CB1R-mediated synaptic plasticity regulate GABAergic and glutamatergic transmission, respectively, and are mediated by retrograde 2-AG signaling [59]. Since the durations of DSE and DSI are determined largely by enzymatic degradation of 2-AG, one might predict that blocking 2-AG hydrolysis would extend the time course of DSE/DSI [46,60]. However, in vitro recordings of neurons revealed that it is mediated by MGL and another enzyme known to modify 2-AG, COX-2, and not by ABHD6 [46,60,61].
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2018, Progress in Lipid ResearchCitation Excerpt :For instance, Kim and Alger showed that inhibition of COX-2 prolonged DSI in hippocampal slice preparations [147]. A later study in cultured hippocampal neurons showed that the duration of DSI in a subpopulation of interneurons was influenced by both MAGL and COX-2 activity [125]. Substrate-selective inhibitors for COX-2 have been developed, which selectively block the oxidation of 2-AG and AEA but not of AA [66,148].