Pharmacological evidence for the involvement of diacylglycerol lipase in depolarization-induced endocanabinoid release

Neuropharmacology. 2008 Jan;54(1):58-67. doi: 10.1016/j.neuropharm.2007.06.002. Epub 2007 Jun 22.


Depolarization-induced suppression of inhibition (DSI) or excitation (DSE) is a well-known form of endocannabinoid-mediated short-term plasticity that is induced by postsynaptic depolarization. It is generally accepted that DSI/DSE is triggered by Ca(2+) influx through voltage-gated Ca(2+) channels. It is also demonstrated that DSI/DSE is mediated by 2-arachidonoylglycerol (2-AG). However, how Ca(2+) induces 2-AG production is still unclear. In the present study, we investigated molecular mechanisms underlying the Ca(2+)-driven 2-AG production. Using cannabinoid-sensitive inhibitory synapses of cultured hippocampal neurons, we tested several inhibitors for enzymes that are supposed to be involved in 2-AG metabolism. The chemicals we tested include inhibitors for phospholipase C (U73122 and ET-18), diacylglycerol kinase (DGK inhibitor 1), phosphatidic acid phosphohydrolase (propranolol), and diacylglycerol lipase (DGL; RHC-80267 and tetrahydrolipstatin (THL)). However, unfavorable side effects were observed with these inhibitors, except for THL. Furthermore, we found that RHC-80267 hardly inhibited the endocannabinoid release driven by G(q/11)-coupled receptors, which is thought to be DGL-dependent. By contrast, THL exhibited no side effects as long as we tested, and was confirmed to inhibit the DGL-dependent process. Using THL as a DGL inhibitor, we demonstrated that DGL is involved in both hippocampal DSI and cerebellar DSE. To test a possible involvement of PLCdelta in DSI, we examined hippocampal DSI in PLCdelta1, delta3 and delta4-knockout mice. However, there was no significant difference in the DSI magnitude between these knockout mice and wild-type mice. The present study clearly shows that DGL is a prerequisite for DSI/DSE. The enzymes yielding DG remain to be determined.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adrenergic beta-Antagonists / pharmacology
  • Animals
  • Animals, Newborn
  • Arachidonic Acids / metabolism
  • Calcium / metabolism
  • Cannabinoid Receptor Modulators / metabolism*
  • Cells, Cultured
  • Electric Stimulation
  • Endocannabinoids
  • Enzyme Inhibitors / pharmacology
  • Glycerides / metabolism
  • Hippocampus / cytology
  • Inhibitory Postsynaptic Potentials / drug effects
  • Inhibitory Postsynaptic Potentials / physiology
  • Lipoprotein Lipase / metabolism*
  • Membrane Potentials / drug effects
  • Membrane Potentials / physiology
  • Membrane Potentials / radiation effects
  • Mice
  • Mice, Knockout
  • Neurons* / drug effects
  • Neurons* / metabolism
  • Neurons* / radiation effects
  • Patch-Clamp Techniques
  • Phospholipase C delta / deficiency
  • Propranolol / pharmacology
  • Rats
  • Rats, Sprague-Dawley


  • Adrenergic beta-Antagonists
  • Arachidonic Acids
  • Cannabinoid Receptor Modulators
  • Endocannabinoids
  • Enzyme Inhibitors
  • Glycerides
  • glyceryl 2-arachidonate
  • Propranolol
  • Lipoprotein Lipase
  • Phospholipase C delta
  • Calcium