Journal of Comparative Physiology A

, Volume 195, Issue 9, pp 831–841 | Cite as

Two forms of long-term depression in a polysynaptic pathway in the leech CNS: one NMDA receptor-dependent and the other cannabinoid-dependent

  • Qin Li
  • Brian D. BurrellEmail author
Original Paper


Although long-term depression (LTD) is a well-studied form of synaptic plasticity, it is clear that multiple cellular mechanisms are involved in its induction. In the leech, LTD is observed in a polysynaptic connection between touch mechanosensory neurons (T cells) and the S interneuron following low frequency stimulation. LTD elicited by 450 s low frequency stimulation was blocked by N-methyl-d-aspartic acid (NMDA) receptor antagonists. However, LTD elicited by 900 s low frequency stimulation was insensitive to NMDA receptor antagonists and was instead dependent on cannabinoid signaling. This LTD was blocked by both a cannabinoid receptor antagonist and by inhibition of diacylglycerol lipase, which is necessary for the synthesis of the cannabinoid transmitter 2-arachidonyl glycerol (2-AG). Bath application of 2-AG or the cannabinoid receptor agonist CP55 940 also induced LTD at this synapse. These results indicate that two forms of LTD coexist at the leech T-to-S polysynaptic pathway: one that is NMDA receptor-dependent and another that is cannabinoid-dependent and that activation of either form of LTD is dependent on the level of activity in this circuit.


Long-term depression NMDA receptor Cannabinoid Leech Synaptic plasticity 



2-Arachidonyl glycerol


α-Amino-3-hydroxy-5-methylisoxazole-4-propionic acid




Analysis of variance


2-Amino-5-phosphonopentanoic acid


Central nervous system


Dimethyl sulfoxide


Excitatory post-synaptic potential


Low frequency stimulation


Long-term depression


Long-term potentiation


Metabotropic glutamate receptor




N-methyl-d-aspartic acid receptor



The authors thank Drs. Brenda Moss, Kenneth Muller, Kevin Crisp and Maurice Elphick for their helpful comments and suggestions. Supported by grants from the National Science Foundation (IBN-0432683, BDB), the South Dakota Spinal Cord/Traumatic Brain Injury Research Council (BDB) and by a subproject of the National Institutes of Health grant (P20 RR015567, BDB), which is designated as a Center of Biomedical Research Excellence (COBRE).

Supplementary material

359_2009_462_MOESM1_ESM.eps (975 kb)
Supplementary Figure 1. The different periods of drug perfusion between preparations that received 450s versus 900s low frequency stimulation did not change the effects of AP5 or AM251 on LTD. AP5 bath-application lasting to 900s (which matches the duration of drug treatment during 900s low frequency stimulation) blocked LTD following 450s low frequency stimulation as effectively as synapses that underwent a 450s drug application that coincided with the 450s low frequency stimulation (one-way ANOVA p<0.001; Newman-Keuls’ test: between 450s and 900s AP5 perfusion vs. no drug, p<0.001*). Neither the 450s nor 900s AM251 perfusion were effective at blocking LTD following 450s low frequency stimulation and neither group differed from synapses that underwent 450s low frequency stimulation in saline with DMSO (one-way ANOVA, ns). DMSO attenuated LTD following 450s low frequency stimulation, but significant depression was still observed. Length of AP5 or AM251 treatment did not alter the effects of either drug on LTD of the electrical synaptic component (Data not shown). (EPS 976 kb)


  1. Anwyl R (2006) Induction and expression mechanisms of postsynaptic NMDA receptor-independent homosynaptic long-term depression. Prog Neurobiol 78(1):17–37PubMedCrossRefGoogle Scholar
  2. Baccus SA (1998) Synaptic facilitation by reflected action potentials: enhancement of transmission when nerve impulses reverse direction at axon branch points. Proc Natl Acad Sci USA 95:8345–8350PubMedCrossRefGoogle Scholar
  3. Baccus SA, Burrell BD, Sahley CL, Muller KJ (2000) Action potential reflection and failure at axon branch points cause stepwise changes in EPSPs in a neuron essential for learning. J Neurophysiol 83:1693–1700PubMedGoogle Scholar
  4. Basavarajappa BS (2007) Critical enzymes involved in endocannabinoid metabolism. Protein Pept Lett 14:237–246PubMedCrossRefGoogle Scholar
  5. Bear MF, Abraham WC (1996) Long-term depression in hippocampus. Annu Rev Neurosci 19:437–462PubMedCrossRefGoogle Scholar
  6. Bender VA, Bender KJ, Brasier DJ, Feldman DE (2006) Two coincidence detectors for spike timing-dependent plasticity in somatosensory cortex. J Neurosci 26:4166–4177PubMedCrossRefGoogle Scholar
  7. Bi G, Poo M (2001) Synaptic modification by correlated activity: Hebb’s postulate revisited. Annu Rev Neurosci 24:139–166PubMedCrossRefGoogle Scholar
  8. Breivogel CS, Griffin G, Di Marzo V, Martin BR (2001) Evidence for a new G protein-coupled cannabinoid receptor in mouse brain. Mol Pharmacol 60:155–163PubMedGoogle Scholar
  9. Brockie PJ, Madsen DM, Zheng Y, Mellem J, Maricq AV (2001) Differential expression of glutamate receptor subunits in the nervous system of Caenorhabditis elegans and their regulation by the homeodomain protein UNC-42. J Neurosci 21:1510–1522PubMedGoogle Scholar
  10. Burke RD, Angerer LM, Elphick MR, Humphrey GW, Yaguchi S, Kiyama T, Liang S, Mu X, Agca C, Klein WH, Brandhorst BP, Rowe M, Wilson K, Churcher AM, Taylor JS, Chen N, Murray G, Wang D, Mellott D, Olinski R, Hallböök F, Thorndyke MC (2006) A genomic view of the sea urchin nervous system. Dev Biol 300:434–460PubMedCrossRefGoogle Scholar
  11. Burrell BD, Li Q (2008) Co-induction of long-term potentiation and long-term depression at a central synapse in the leech. Neurobiol Learn Mem 90:275–279PubMedCrossRefGoogle Scholar
  12. Burrell BD, Sahley CL (2004) Multiple forms of long-term potentiation and long-term depression converge on a single interneuron in the leech CNS. J Neurosci 24:4011–4019PubMedCrossRefGoogle Scholar
  13. Burrell BD, Sahley CL, Muller KJ (2003) Progressive recovery of learning during regeneration of a single synapse in the medicinal leech. J Comp Neurol 457(1):67–74PubMedCrossRefGoogle Scholar
  14. Cachope R, Mackie K, Triller A, O’Brien J, Pereda AE (2007) Potentiation of electrical and chemical synaptic transmission mediated by endocannabinoids. Neuron 56:1034–1047PubMedCrossRefGoogle Scholar
  15. Chevaleyre V, Takahashi KA, Castillo PE (2007) Endocannabinoid-mediated synaptic plasticity in the CNS. Annu Rev Neurosci 29:37–76CrossRefGoogle Scholar
  16. Crisp KM, Muller KJ (2006) A 3-synapse positive feedback loop regulates the excitability of an interneuron critical for sensitization in the leech. J Neurosci 26:3524–3531PubMedCrossRefGoogle Scholar
  17. De Petrocellis L, Melck D, Bisogno T, Milone A, Di Marzo V (1999) Finding of the encocannabinoid signaling system in Hydra, a very primitive organism: possible role in the feeding response. Neurosci 92:377–387CrossRefGoogle Scholar
  18. Di Marzo V, Bisogno T, De Petrocellis L, Melck D, Martin BR (1999) Cannabimimetic fatty acid derivatives: the anandamide family and other endocannabinoids. Curr Med Chem 6:721–744PubMedGoogle Scholar
  19. Egertova M, Elphick MR (2007) Localization of CiCBR in the invertebrate chordate Ciona intestinalis: evidence of an ancient role for cannabinoid receptors as axonal regulators of neuronal signalling. J Comp Neurol 502:660–672PubMedCrossRefGoogle Scholar
  20. Eliot LS, Hawkins RD, Kandel ER, Schacher S (1994) Pairing-specific, activity-dependent presynaptic facilitation at Aplysia sensory-motor neuron synapses in isolated cell culture. J Neurosci 14:368–383PubMedGoogle Scholar
  21. Elphick MR (1998) An invertebrate G-protein coupled receptor is a chimeric cannabinoid/melanocortin receptor. Brain Res 780:168–171PubMedCrossRefGoogle Scholar
  22. Elphick MR, Egertová M (2001) The neurobiology and evolution of cannabinoid signalling. Philos Trans R Soc Lond B Biol Sci 356:381–408PubMedCrossRefGoogle Scholar
  23. Elphick MR, Egertova M (2005) The phylogenetic distribution and evolutionary origins of endocannabinoid signalling. Handb Exp Pharmacol 168:283–297PubMedCrossRefGoogle Scholar
  24. Elphick MR, Satou Y, Satoh N (2003) The invertebrate ancestry of endocannabinoid signalling: an orthologue of vertebrate cannabinoid receptors in the urochordate Ciona intestinalis. Gene 302:95–101PubMedCrossRefGoogle Scholar
  25. Ezzeddine Y, Glanzman DL (2003) Prolonged habituation of the gill-withdrawal reflex in Aplysia depends on protein synthesis, protein phosphatase activity and postsynaptic glutamate receptors. J Neurosci 23:9585–9594PubMedGoogle Scholar
  26. Frank E, Jansen JK, Rinvik E (1975) A multisomatic axon in the central nervous system of the leech. J Comp Neurol 159:1–13PubMedCrossRefGoogle Scholar
  27. Friesen WO (1981) Physiology of water motion detection in the medicinal leech. J Physiol 92:255–275Google Scholar
  28. Gavrila LB, Orth PM, Charlton MP (2005) Phosphorylation-dependent low-frequency depression at phasic synapses of a crayfish motoneuron. J Neurosci 25:3168–3180CrossRefGoogle Scholar
  29. Grey KB, Moss BL, Burrell BD (2009) Molecular identification and expression of the NMDA receptor NR1 subunit in the leech. Invert Neurosci 9:11–20PubMedCrossRefGoogle Scholar
  30. Guo HF, Zhong Y (2006) Requirement of Akt to mediate long-term synaptic depression in Drosophila. J Neurosci 26:4004–4014PubMedCrossRefGoogle Scholar
  31. Ha TJ, Kohn AB, Bobkova YV, Moroz LL (2006) Molecular characterization of NMDA-like receptors in Aplysia and Lymnaea: relevance to memory mechanisms. Biol Bull 210:255–270PubMedCrossRefGoogle Scholar
  32. Hajos N, Ledent C, Freund TF (2001) Novel cannabinoid-sensitive receptor mediates inhibition of glutamatergic synaptic transmission in the hippocampus. Neurosci 106:1–4CrossRefGoogle Scholar
  33. Hashimotodani Y, Ohno-Shosaku T, Kano M (2007) Endocannabinoids and synaptic function in the CNS. Neuroscientist 13:127–137PubMedCrossRefGoogle Scholar
  34. Heifets BD, Chevaleyre V, Castillo PE (2008) Interneuron activity controls endocannabinoid-mediated presynaptic plasticity through calcineurin. Proc Natl Acad Sci USA 105:10250–10255PubMedCrossRefGoogle Scholar
  35. Jami SA, Wright WG, Glanzman DL (2007) Differential classical conditioning of the gill-withdrawal reflex in Aplysia recruits both NMDA receptor-dependent enhancement and NMDA receptor-dependent depression of the reflex. J Neurosci 27:3064–3068PubMedCrossRefGoogle Scholar
  36. Kristan WB Jr, Calabrese RL, Friesen WO (2005) Neuronal control of leech behavior. Prog Neurobiol 76:279–327PubMedCrossRefGoogle Scholar
  37. Lemak MS, Bravarenko NI, Bobrov MY, Bezuglov VV, Ierusalimsky VN, Storozhuk MV, Malyshev AY, Balaban PM (2007) Cannabinoid regulation in identified synapse of terrestrial snail. Eur J Neurosci 26:3207–3214PubMedCrossRefGoogle Scholar
  38. Leung HT, Tseng-Crank J, Kim E, Mahapatra C, Shino S, Zhou Y, An L, Doerge RW, Pak WL (2008) DAG lipase activity is necessary for TRP channel regulation in Drosophila photoreceptors. Neuron 58:884–896PubMedCrossRefGoogle Scholar
  39. Li Q, Burrell BD (2008) CNQX and AMPA inhibit electrical synaptic transmission: a potential interaction between electrical and glutamatergic synapses. Brain Res 1228:43–57PubMedCrossRefGoogle Scholar
  40. Linden DJ (1994) Long-term synaptic depression in the mammalian brain. Neuron 2:457–472CrossRefGoogle Scholar
  41. Lynn BD, Rempel JL, Nagy JI (2001) Enrichment of neuronal and glial connexins in the postsynaptic density subcellular fraction of rat brain. Brain Res 898:1–8PubMedCrossRefGoogle Scholar
  42. Macagno ER, Muller KJ, Pitman RM (1987) Conduction block silences parts of a chemical synapse in the central nervous system. J Physiol 387:649–664PubMedGoogle Scholar
  43. Mackie K (2006) Mechanisms of CB1 receptor signaling: endocannabinoid modulation of synaptic strength. Int J Obes (Lond) 30(Suppl 1):S19–S23CrossRefGoogle Scholar
  44. Magni F, Pellegrino M (1978) Patterns of activity and the effects of activation of the fast conducting system on the behaviour of unrestrained leeches. J Exp Biol 76:123–135PubMedGoogle Scholar
  45. Malenka RC, Bear MF (2004) LTP and LTD: an embarrassment of riches. Neuron 44:5–21PubMedCrossRefGoogle Scholar
  46. Matias I, Bisogno T, Melck D, Vandenbulcke F, Verger-Bocquet M, De Petrocellis L, Sergheraert C, Breton C, Di Marzo V, Salzet M (2001) Evidence for an endocannabinoid system in the central nervous system of the leech Hirudo medicinalis. Brain Res Mol Brain Res 87:145–159PubMedCrossRefGoogle Scholar
  47. McPartland JM (2004) Phylogenomic and chemotaxonomic analysis of the endocannabinoid system. Brain Res Rev 45(1):18–29PubMedCrossRefGoogle Scholar
  48. McPartland JM, Di Marzo V, De Petrocellis L, Mercer A, Glass M (2001) Cannabinoid receptors are absent in insects. J Comp Neurol 436:423–429PubMedCrossRefGoogle Scholar
  49. McPartland JM, Agraval J, Gleeson D, Heasman K, Glass M (2006) Cannabinoid receptors in invertebrates. J Evol Biol 19:366–373PubMedCrossRefGoogle Scholar
  50. Modney BK, Sahley CL, Muller KJ (1997) Regeneration of a central synapse restores nonassociative learning. J Neurosci 17:6478–6482PubMedGoogle Scholar
  51. Morishita W, Malenka RC (2008) Mechanisms underlying dedepression of synaptic NMDA receptors in the hippocampus. J Neurophysiol 99:254–263PubMedCrossRefGoogle Scholar
  52. Muller KJ, Scott SA (1981) Transmission at a ‘direct’ electrical connexion mediated by an interneurone in the leech. J Physiol 311:565–583PubMedGoogle Scholar
  53. Oliet SH, Malenka RC, Nicoll RA (1997) Two distinct forms of long-term depression coexist in CA1 hippocampal pyramidal cells. Neuron 18:969–982PubMedCrossRefGoogle Scholar
  54. Peterson EL (1984) The fast conducting system of the leech: a network of 93 dye-coupled interneurons. J Comp Physiol 154:781–788CrossRefGoogle Scholar
  55. Phelan P (2005) Innexins: members of an evolutionarily conserved family of gap-junction proteins. Biochim Biophys Acta 1711:225–245PubMedCrossRefGoogle Scholar
  56. Rash JE, Staines WA, Yasumura T, Patel D, Furman CS, Stelmack GL, Nagy JI (2000) Immunogold evidence that neuronal gap junctions in adult rat brain and spinal cord contain connexin-36 but not connexin-32 or connexin-43. Proc Natl Acad Sci USA 97:7573–7578PubMedCrossRefGoogle Scholar
  57. Rawls SM, Rodriguez T, Baron DA, Raffa RB (2006) A nitric oxide synthase inhibitor (L-NAME) attenuates abstinence-induced withdrawal from both cocaine and a cannabinoid agonist (WIN 55212-2) in Planaria. Brain Res 1099:82–87PubMedCrossRefGoogle Scholar
  58. Rawls SM, Gomez T, Raffa RB (2007) An NMDA antagonist (LY 235959) attenuates abstinence-induced withdrawal of planarians following acute exposure to a cannabinoid agonist (WIN 55212-2). Pharmacol Biochem Behav 86:499–504PubMedCrossRefGoogle Scholar
  59. Sahley CL, Modney BK, Boulis NM, Muller KJ (1994) The S cell: an interneuron essential for sensitization and full dishabituation of leech shortening. J Neurosci 14:6715–6721PubMedGoogle Scholar
  60. Salzet M, Stefano GB (2002) The endocannabinoid system in invertebrates. Prostaglandins Leukot Essent Fatty Acids 66:353–361PubMedCrossRefGoogle Scholar
  61. Sjöström PJ, Turrigiano GG, Nelson SB (2007) Multiple forms of long-term plasticity at unitary neocortical layer 5 synapses. Neuropharmacology 52:176–184PubMedCrossRefGoogle Scholar
  62. Smith M, Pereda AE (2003) Chemical synaptic activity modulates nearby electrical synapses. Proc Natl Acad Sci USA 100:4849–4854PubMedCrossRefGoogle Scholar
  63. Sotelo C, Korn H (1978) Morphological correlates of electrical and other interactions through low-resistance pathways between neurons of the vertebrate central nervous system. Int Rev Cytol 55:67–107PubMedCrossRefGoogle Scholar
  64. Stefano GB, Salzet B, Salzet M (1997) Identification and characterization of the leech CNS cannabinoid receptor: coupling to nitric oxide release. Brain Res 753:219–224PubMedCrossRefGoogle Scholar
  65. Tzounopoulos T, Rubio ME, Keen JE, Trussell LO (2007) Coactivation of pre- and postsynaptic signaling mechanisms determines cell-specific spike-timing-dependent plasticity. Neuron 54:291–301PubMedCrossRefGoogle Scholar
  66. Ultsch A, Schuster CM, Laube B, Betz H, Schmitt B (1993) Glutamate receptors of Drosophila melanogaster. Primary structure of a putative NMDA receptor protein expressed in the head of the adult fly. FEBS Lett 324:171–177PubMedCrossRefGoogle Scholar
  67. Weeks JC (1982) Segmental specialization of a leech swim-initiating interneuron, cell 2051. J Neurosci 2:972–985PubMedGoogle Scholar
  68. Wiley JL, Barrett RL, Lowe J, Balster RL, Martin BR (1995) Discriminative stimulus effects of CP 55,940 and structurally dissimilar cannabinoids in rats. Neuropharmacology 34:669–676PubMedCrossRefGoogle Scholar
  69. Xia S, Miyashita T, Fu TF, Lin WY, Wu CL, Pyzocha L, Lin IR, Saitoe M, Tully T, Chiang AS (2005) NMDA receptors mediate olfactory learning and memory in Drosophila. Curr Biol 15:603–615PubMedCrossRefGoogle Scholar
  70. Zannat MT, Locatelli F, Rybak J, Menzel R, Leboulle G (2006) Identification and localisation of the NR1 sub-unit homologue of the NMDA glutamate receptor in the honeybee brain. Neurosci Lett 398:274–279PubMedCrossRefGoogle Scholar
  71. Zoidl G, Petrasch-Parwez E, Ray A, Meier C, Bunse S, Habbes HW, Dahl G, Dermietzel R (2007) Localization of the pannexin1 protein at postsynaptic sites in the cerebral cortex and hippocampus. Neuroscience 146:9–16PubMedCrossRefGoogle Scholar

Copyright information

© Springer-Verlag 2009

Authors and Affiliations

  1. 1.Neuroscience Group, Division of Basic Biomedical SciencesSanford School of Medicine at the University of South DakotaVermillionUSA

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