title: New considerations on the neuromodulatory role of thiamine.
abstract: BACKGROUND
  A nonmetabolic role for thiamine in cholinergic neurotransmission has long been suggested. The mechanism remains unclear. We sought to extend our previous research to elucidate the effect of the thiamine metabolic antagonist, oxythiamine, on the release of acetylcholine from the brain.
  
  
  METHODS
  The potassium-stimulated release of acetylcholine from superfused rat brain slices was determined. Hand-cut slices of cerebral cortex were preincubated with tritiated choline to label acetylcholine stores. Two periods of stimulation (S1, S2) with 50 mmol/l solution for 3.5 min were performed as superfusate was collected. During S1, only 50 mmol/l potassium-containing Krebs-bicarbonate buffer with 2 mmol/l calcium was used. Using a two-by-two design, S2 consisted of exposure to 50 mmol/l potassium with or without 10(-4) mol/l oxythiamine, with or without calcium. The S2/S1 ratio was calculated.
  
  
  RESULTS
  Oxythiamine enhanced the potassium-evoked release of acetylcholine by 60% but only when calcium was present in the superfusing medium.
  
  
  CONCLUSIONS
  These data confirm earlier findings with oxythiamine on the calcium-mediated synaptic transmission of acetylcholine and support a possible neuromodulatory role for thiamine distinct from its actions as a cofactor during metabolic processes.
authors.affiliation: Department of Pharmaceutical Science, St. John's University, New York, NY, USA. jhirschphd@nyc.rr.com
authors.forename: Joseph A
authors.initials: JA
authors.lastname: Hirsch
authors.forename: James
authors.initials: J
authors.lastname: Parrott
mesh_terms: D000109:Acetylcholine / Q000378:metabolism*; D000818:Animals; D000963:Antimetabolites / Q000494:pharmacology; D002118:Calcium / Q000494:pharmacology; D002540:Cerebral Cortex / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D066298:In Vitro Techniques; D008297:Male; D010119:Oxythiamine / Q000494:pharmacology; D011188:Potassium / Q000819:agonists / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology*; D013831:Thiamine / Q000037:antagonists & inhibitors / Q000502:physiology*
chemical_list: D000963:Antimetabolites; D010119:Oxythiamine; D000109:Acetylcholine; D011188:Potassium; D002118:Calcium; D013831:Thiamine