Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2007 Jun 7;54(5):801-12.
doi: 10.1016/j.neuron.2007.05.020.

Endocannabinoid-mediated long-term plasticity requires cAMP/PKA signaling and RIM1alpha

Vivien Chevaleyre  1 , Boris D Heifets, Pascal S Kaeser, Thomas C Südhof, Pablo E Castillo
Affiliations

Endocannabinoid-mediated long-term plasticity requires cAMP/PKA signaling and RIM1alpha

Vivien Chevaleyre et al. Neuron. .

Erratum in

  • Neuron. 2007 Jul 5;55(1):169. Purpura, Dominick P [removed]

Abstract

Endocannabinoids (eCBs) have emerged as key activity-dependent signals that, by activating presynaptic cannabinoid receptors (i.e., CB1) coupled to G(i/o) protein, can mediate short-term and long-term synaptic depression (LTD). While the presynaptic mechanisms underlying eCB-dependent short-term depression have been identified, the molecular events linking CB1 receptors to LTD are unknown. Here we show in the hippocampus that long-term, but not short-term, eCB-dependent depression of inhibitory transmission requires presynaptic cAMP/PKA signaling. We further identify the active zone protein RIM1alpha as a key mediator of both CB1 receptor effects on the release machinery and eCB-dependent LTD in the hippocampus. Moreover, we show that eCB-dependent LTD in the amygdala and hippocampus shares major mechanistic features. These findings reveal the signaling pathway by which CB1 receptors mediate long-term effects of eCBs in two crucial brain structures. Furthermore, our results highlight a conserved mechanism of presynaptic plasticity in the brain.

PubMed Disclaimer

Figures

Figure 1
Figure 1
Endocannabinoid-mediated long-term, but not short-term, plasticity requires cAMP/PKA signaling. (A) A persistent increase in cAMP level by incubation (>30 min) and continuous bath application of the adenylyl cyclase activator forskolin (10 μM) blocked I-LTD. (B) Incubation and continous application of either of two different PKA inhibitors (10 μM H-89, n = 4; 1 μm PKI 14-22 amide, n = 7) also impaired I-LTD induction. Direct application of a membrane impermeant PKA blocker (1 μM PKI 6-22 amide, n = 7 cells, 5 mice) to the postsynaptic pyramidal cell, via recording pipette, did not affect I-LTD. (C) None of these manipulations interfered with DSI. Averaged sample traces taken at times indicated by numbers are shown on the right.
Figure 2
Figure 2
CB1 receptors target the release machinery via the cAMP/PKA pathway. (A) WIN application depressed mIPSC frequency, an effect blocked by CB1 receptor antagonists (2 μM AM 251, n = 2; 10 μM SR141716, n = 3). Sample traces before and during WIN application are shown at right. (B) WIN had no effect on mIPSC amplitude. (C) The WIN-mediated depression of mIPSC frequency is blocked in the continuous presence of forskolin (n = 6) or H89 (n = 5).
Figure 3
Figure 3
Long-term, but not short-term, eCB-mediated plasticity requires the presynaptic active zone protein RIM1α. (A) TBS delivered in slices from RIM1α KO mice triggered no depression compared to the I-LTD obtained in WT littermates (n = 18, 10 mice and n = 14, 9 mice respectively). (B) In contrast, DSI was identical in both WT and KO animals. Averaged sample traces are shown above (A) or on the right (B).
Figure 4
Figure 4
Altered basal transmission at excitatory or inhibitory synapses cannot explain the lack of I-LTD in RIM1α KO mice. (A) Pharmacological induction of I-LTD by DHPG (50 μM, 10 min) was normal in WT mice (n = 5 cells, 4 mice) but impaired in RIM1α KO mice (n = 5 cells, 4 mice).(B) Similarly, application of the CB1 receptor agonist WIN (5 µM, 25 min) subsequently chased with the CB1 receptor antagonist SR 141716 (5 µM) induced a lasting depression of field IPSPs in WT (n = 4, 3 mice) but not in RIM1α KO mice (n = 5, 3 mice). Sample traces before, following WIN application, and in 100 µM picrotoxin are shown at right. (C) The average IPSC amplitude (excluding transmission failures), the failure rate and the paired-pulse ratio (IPSC2/IPSC1) at CB1R+ fibers isolated by focal stimulation were identical in WT (10 cells, 10 mice) and RIM1α KO mice (13 cells, 11 mice).
Figure 5
Figure 5
PKA regulation of GABA release at CB1+ fibers requires RIM1α. (A) Representative experiments showing the effect of H-89 in WT and RIM1α KO mice using focal stimulation of CB1R+ fibers. Averaged sample traces at times indicated by numbers are shown on the right. (B) Summary graph showing significantly greater depression of synaptic transmission (IPSC amplitude, including failures) by H-89 in WT vs. RIM1α KO mice (8 cells, 8 mice; 9 cells, 8 mice respectively). Without drug application, no significant depression was observed over time. (C) H-89 significantly increased failure rate and aired-pulse ratio (IPSC2/IPSC1) in WT, but not RIM1α KO mice (same cells as B).
Figure 6
Figure 6
RIM1α mediates CB1 receptor action on the release machinery. (A) Sample trace before and after WIN application in WT and RIM1α KO mice. (B) Averaged mIPSC frequency plot before and after WIN application in WT (4 cells, 3 animals) and RIM1α KO mice (5 cells, 3 animals). (C) Histogram of mIPSC frequency showing the lack of effect of WIN in RIM1α KO mice.
Figure 7
Figure 7
RIM1α and PKA control GABA release and inhibitory synaptic plasticity in basolateral amygdala. (A) WIN depressed mIPSC frequency in BLA (n = 5), an effect blocked by CB1 receptor antagonists (5 μM AM 251, n = 2; 5 μM SR131716, n = 2). Sample traces are shown on the right. (B) WIN-mediated depression was blocked by H-89 (n =5). (C) LTD induction was blocked in RIM1α KO mice (11 cells, 5 mice), compared to their WT littermates (9 cells, 6 mice). (D) LTD induced pharmacologically by DHPG (50 µM, 15 min) was also abolished in RIM1α KO mice compared to WT mice (n = 7, 3 WT mice and n = 6, 4 KO mice).
Figure 8
Figure 8
Model of the divergent signaling pathways downstream of the CB1 receptor that triggers eCB-mediated short- or long-term depression. During eCB-mediated short-term depression, brief activation of CB1 receptors reversibly depresses neurotransmitter release mainly by blocking presynaptic VGCC, presumably via Gβ/γ subunits. In contrast, during the induction of eCB-mediated LTD, a longer-lasting (i.e., few minutes) (Chevaleyre and Castillo, 2003; Ronesi et al., 2004) activation of CB1 receptors inhibits adenylyl cyclase (AC) activity via Gα subunits, thereby reducing presynaptic cAMP levels and PKA activity. This modification “gates” an enduring change of the release machinery that requires the active zone protein RIM1α. PKA may directly phosphorylate RIM1α and/or other associated proteins.
See this image and copyright information in PMC

References

    1. Alger BE. Retrograde signaling in the regulation of synaptic transmission: focus on endocannabinoids. Prog Neurobiol. 2002;68:247–286. - PubMed
    1. Alger BE, Pitler TA, Wagner JJ, Martin LA, Morishita W, Kirov SA, Lenz RA. Retrograde signalling in depolarization-induced suppression of inhibition in rat hippocampal CA1 cells. J Physiol. 1996;496(Pt 1):197–209. - PMC - PubMed
    1. Arai A, Silberg J, Lynch G. Differences in the refractory properties of two distinct inhibitory circuitries in field CA1 of the hippocampus. Brain Res. 1995;704:298–306. - PubMed
    1. Azad SC, Eder M, Marsicano G, Lutz B, Zieglgansberger W, Rammes G. Activation of the cannabinoid receptor type 1 decreases glutamatergic and GABAergic synaptic transmission in the lateral amygdala of the mouse. Learn Mem. 2003;10:116–128. - PMC - PubMed
    1. Azad SC, Monory K, Marsicano G, Cravatt BF, Lutz B, Zieglgansberger W, Rammes G. Circuitry for associative plasticity in the amygdala involves endocannabinoid signaling. J Neurosci. 2004;24:9953–9961. - PMC - PubMed

Publication types

MeSH terms

LinkOut - more resources