Anandamide potentiation of miniature spontaneous excitatory synaptic transmission is mediated via IP3 pathway

Abstract

Although arachidonoyl ethanolamide (AEA or anandamide) is the first identified endocannabinoid, its roles in synaptic signaling and neuronal survival are still controversial. Here we report that AEA induced a dose-dependent elevation of the frequency of miniature excitatory postsynaptic currents (mEPSCs) in mouse hippocampal neurons in culture. This potentiation was not blocked by SR141716 or AM251, selective cannabinoid receptor antagonists), indicating that the AEA elevation of mEPSCs is not mediated via the CB1 receptor. Similarly, capsazepine and iodoresiniferatoxin, selective vanilloid receptor antagonists, and ryanodine also failed to inhibit the effect of AEA on mEPSCs. However, 2-APB and Xestospongin C, IP3 inhibitors, significantly attenuated AEA-induced increase in hippocampal excitatory synaptic transmission. Application of 3-deoxy-3-fluoro-D-myo-inositol 1,4,5-trisphosphate enhanced the frequency of mEPSCs and occluded the effect of AEA on mEPSCs. Our results suggest that AEA-produced stimulatory effect on excitatory glutamatergic synaptic transmission is likely mediated via an IP3 pathway. Keywordsendocannabinoids; cannabinoid receptors; vanilloid receptor; ryanodine receptor; excitatory postsynaptic currents; hippocampus Endocannabinoids (eCBs) are endogenous signaling mediators and have been demonstrated to be involved in a variety of physiological, pharmacological and pathological processes (Alger, 2002;Bisogno et al., 2008;Chevaleyre et al., 2006;Cinar et al., 2008;Freund et al., 2003;Hájos and Freund, 2002;Mackie, 2006;Páldyová et al., 2008;Páldy et al., 2008;Piomelli, 2003;Sarne and Mechoulam, 2005;van der Stelt and Di Marzo, 2005). Arachidonoyl ethanolamide (AEA or anandamide) is the first identified endogenous ligand for G proteincoupled cannabinoid receptors (Devane et al., 1992). Despite a similar chemical structure of AEA and second endogenous ligand for the cannabinoid receptor, 2-arachidonoyl glycerol (2-AG) (Mechoulam et al., 1995;Stella et al., 1997), they have very different pathways for their synthesis and degradation (Freund et al., 2003;Kozak et al., 2004;Mackie, 2006;Piomelli, 2003;Sugiura et al., 2006). For instance, 2-AG is mainly produced from diacylglycerol (DAG) by diacylglycerol lipase (DGL) and hydrolyzed to arachidonic acid (AA) by monoacylglycerol lipase (MGL), whereas AEA is largely synthesized from Narachidonoylphosphatidylethanolamine (NAPE) by phospholipase D (PLD) and degraded to AA by fatty acid amide hydrolase (FAAH). Also the enzymes that synthesize 2-AG are present in postsynaptic dendritic spines (Katona et al., 2006;Yoshida et al., 2006) that make AEA appear to be present in presynaptic terminals (Nyilas et al., 2008). In addition, AEA is a partial CB1 receptor and a weak CB2 receptor agonist, and an agonist for the vanilloid receptor (De Petrocellis and Di Marzo, 2005;Ross, 2003;Zygmunt et al., 1999), whereas 2-AG is a full agonist for both CB1 and CB2 receptors (Bisogno et al., 2005;Freund et al., 2003;Piomelli, 2003;Sugiura et al., 2006). In particu...

Functional effects of cannabinoids during dopaminergic specification of human neural precursors derived from induced pluripotent stem cells

“…Huang et al showed the reduction of synaptic transmission on corticostriatal brain slices by application of 20-μM AEA (Huang et al, 2001). Lower AEA concentrations instead, seem to potentiate synaptic transmission as shown by Sang et al (2010) on primary hippocampal neuron cultures. In pharmacologically relevant concentrations, endocannabinoids are also known to modulate functional properties of voltage-gated ion channels including Na + and K + channels (Oz, 2006).…”

Endocannabinoid 2-arachidonoylglycerol protects neurons against β-amyloid insults

“…Primary hippocampal neurons from rat (Sprague Dawley) embryos (E18) or P0 were cultured as described previously (Sang et al, 2005; 2007; Zhang & Chen, 2008, Sang et al, 2010), according to the guidelines approved by the Institutional Animal Care and Use Committee of of Louisiana State University Health Sciences Center in New Orleans. Briefly, after suffocation with carbon dioxide, unconscious animals were decapitated.…”

Supply and demand for endocannabinoids

“…A major synthetic enzyme for anandamide, N-acylphosphatidylethanolamine-specific phospholipase D (NAPE-PLD) [120] is found in some glutamatergic nerve terminals, but not postsynaptic pyramidal cell bodies [121][122], arguing against its being the source of anandamide in either TRPV1-mediated LTD [119] [54], or CB1R-mediated homeostatic plasticity [53]. The association of NAPE-PLD with intracellular, perhaps Ca 2+ -containing cisternae [121], might explain the recent finding that anandamide can induce quantal glutamate release via a CB1R- and TRPV1-independent mechanism [123]. Working out the biosynthetic mechanisms [124] of anandamide production and its modes of action are pressing tasks for the future.…”