title: Modulation of inhibitory neurotransmission by the vanilloid receptor type 1 (TRPV1) in organotypically cultured mouse substantia gelatinosa neurons.
abstract: The vanilloid receptor type 1 (TRPV1) plays a pivotal role in modulating thermal, chemical, and inflammatory pain. TRPV1s are expressed in some dorsal horn (DH) neurons, but their contribution, if any, to central pain processing still remains unclear. We studied the effects of 2microM capsaicin-induced TRPV1 activation in organotypically cultured substantia gelatinosa neurons from post-natal (8-12) mice. Capsaicin affected sIPSC frequency (272+/-60% of control, n=14, P<0.02), but not amplitude (131+/-12% of control, n=14, P>0.05) in patch clamp recordings, also in the presence of 50microM AP-5 (frequency: 265+/-69% of control; n=8, P<0.05; amplitude: 156+/-28% of control; n=8, P>0.05). The frequency increase was reduced by TTX (181+/-21% of control; n=12, P<0.05). Pre-administration of I-RTX (1microM), a TRPV1 antagonist, prevented the capsaicin effect (frequency: 149+/-28% of control, P>0.05, n=12; amplitude: 97+/-4% of control, P>0.05, n=12). NADA (1microM), an endovanilloid/endocannabinoid agonist of TRPV1, induced a significant increase of sISPC frequency (191+/-40% of control; n=8, P<0.05) without affecting the amplitude (102+/-6% of control; n=8, P>0.05), and the co-application of two naturally occurring N-acyldopamines, PALDA (5microM) and STEARDA (5microM) that facilitate the effect of TRPV1 agonists, also induced a significant increase of sIPSC frequency (278+/-67% of control, n=6, P<0.05). The presence of TRPV1 protein and mRNA in DH neurons was confirmed by histological (immunocytochemistry, in situ PCR) and biochemical (Western blotting, PCR) procedures. These data show that TRPV1 modulates inhibitory neurotransmission in cultured substantia gelatinosa neurons, and suggest that endogenous agonists can activate the spinal receptors in vivo.
authors.affiliation: Department of Veterinary Morphophysiology, Via Leonardo da Vinci 44, 10095 Grugliasco, Italy Istituto Nazionale di Neuroscienze, Corso Raffaello 30, 10125 Turin, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Ferrini
authors.forename: Chiara
authors.initials: C
authors.lastname: Salio
authors.forename: Laura
authors.initials: L
authors.lastname: Lossi
authors.forename: Graziana
authors.initials: G
authors.lastname: Gambino
authors.forename: Adalberto
authors.initials: A
authors.lastname: Merighi
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002211:Capsaicin / Q000494:pharmacology; D002478:Cells, Cultured; D007150:Immunohistochemistry; D053444:Inhibitory Postsynaptic Potentials / Q000187:drug effects / Q000502:physiology; D051379:Mice; D009433:Neural Inhibition / Q000187:drug effects / Q000502:physiology*; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D020133:Reverse Transcriptase Polymerase Chain Reaction; D018709:Statistics, Nonparametric; D013376:Substantia Gelatinosa / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology*; D050916:TRPV Cation Channels / Q000037:antagonists & inhibitors / Q000378:metabolism*
chemical_list: D050916:TRPV Cation Channels; C493921:TRPV1 protein, mouse; D002211:Capsaicin
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