title: Modulation of TTX-sensitive voltage-dependent Na+ channels by β-bungarotoxin in rat cerebellar neurons.
abstract: BACKGROUND
  The modulation of voltage-dependent Na+ channels by lipid metabolites such as arachidonic acid or eicosanoids plays a role in physiological functions as well as in degenerative diseases. So far TTX-resistant channels were found mainly to be regulated by lipid metabolites.
  
  
  RESULTS
  We investigated the lipid-dependent modulation of TTX-sensitive (TTX-s) Na+ channels using β-bungarotoxin (β-BuTX, 10 pM), which has an intrinsic phospholipase-A2 activity, and indomethacin (10 μM), which blocks cyclooxygenase activity in primary cerebellar neurons. To investigate TTX-s Na+ channels, whole-currents were measured under K+-free conditions and blocked by 10 nM TTX. The currents resulting from calculating the difference of currents measured in the presence and the absence of TTX were used for further analysis. Application of indomethacin mainly changed the current kinetics but has only minor effects on voltage-dependence. In contrast β-BuTX increased the maximal current amplitude and shifted the voltage-dependent activation towards more negative potentials. The effects of β-BuTX were blocked by indomethacin. Analysis of lipid metabolites which accumulate by treatment with β-BuTX using MALDI-TOF MS showed an increase of cyclooxygenase reaction products in relation to arachidonic acid.
  
  
  CONCLUSIONS
  In summary, we conclude that TTX-sensitive Na+ channels can be directly modulated by cyclooxygenase reaction products leading to higher activity at less depolarized potentials and subsequent higher excitability of neurons. Since activation of cyclooxygenase is also involved in pathways leading to apoptotic cells death this could play a role in degenerative diseases of the CNS and highlights a possible protective effect of cyclooxygenase inhibition.
authors.affiliation: Experimental Ophthalmology, Eye Hospital, University Medical Center Regensburg, Franz-Josef-Strauss Allee 11, 93053 Regensburg, Germany.
authors.forename: Da
authors.initials: D
authors.lastname: Guo
authors.forename: Wei
authors.initials: W
authors.lastname: Xiang
authors.forename: Angela
authors.initials: A
authors.lastname: Seebahn
authors.forename: Cord-Michael
authors.initials: CM
authors.lastname: Becker
authors.forename: Olaf
authors.initials: O
authors.lastname: Strauss
mesh_terms: D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D002038:Bungarotoxins / Q000494:pharmacology*; D002478:Cells, Cultured; D002531:Cerebellum / Q000187:drug effects* / Q000378:metabolism; D016861:Cyclooxygenase Inhibitors / Q000494:pharmacology; D007213:Indomethacin / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects; D009474:Neurons / Q000187:drug effects* / Q000378:metabolism; D018408:Patch-Clamp Techniques; D051381:Rats; D026941:Sodium Channel Blockers / Q000494:pharmacology; D015222:Sodium Channels / Q000378:metabolism*; D013779:Tetrodotoxin / Q000494:pharmacology*
chemical_list: D002038:Bungarotoxins; D016861:Cyclooxygenase Inhibitors; D026941:Sodium Channel Blockers; D015222:Sodium Channels; D013779:Tetrodotoxin; D007213:Indomethacin