title: Evidence of presynaptic and postsynaptic action of local anesthetics in rats.
abstract: OBJECTIVE
  To assess the probable actions of ropivacaine, 50% enantiomeric excess bupivacaine mixture (S75-R25) and levobupivacaine on neuromuscular transmission in vitro.
  
  
  METHODS
  Thirty rats were distributed into groups (n=5) according to the drug used: ropivacaine, bupivacaine (S75-R25) and levobupivacaine. The concentration used for the three local anesthetics (LA) was 5 µg.mL. (-1)The following parameters were evaluated: 1) LA effects on membrane potential (MP) and miniature end plate potential (MEPP). A chick biventer cervicis preparation was also used to evaluate LA effects on the contracture response to acetylcholine.
  
  
  RESULTS
  LA did not alter MP values and decreased the frequency and amplitude of MEPP. In a chick biventer cervicis preparation, bupivacaine (S75-R25) and levobupivacaine decreased the contracture response to acetylcholine with statistical significance, in comparison to ropivacaine.
  
  
  CONCLUSIONS
  In the concentrations used, levobupivacaine and bupivacaine (S75-R25) exhibited presynaptic and postsynaptic actions evidenced by alterations in miniature end plate potentials and contracture response to acetylcholine. Ropivacaine only had a presynaptic action.
authors: Angélica de Fátima de Assunção
authors: Ade F
authors: Braga
authors: Vanessa Henriques
authors: VH
authors: Carvalho
authors: Franklin Sarmento da Silva
authors: FS
authors: Braga
authors: Gloria Maria Braga
authors: GM
authors: Potério
authors: Filipe Nadir Caparica
authors: FN
authors: Santos
mesh_terms: D000109:Acetylcholine / Q000008:administration & dosage / Q000494:pharmacology; D000577:Amides / Q000008:administration & dosage / Q000494:pharmacology*; D000779:Anesthetics, Local / Q000008:administration & dosage / Q000494:pharmacology*; D000818:Animals; D002045:Bupivacaine / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000494:pharmacology*; D000077554:Levobupivacaine; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D051381:Rats; D017208:Rats, Wistar; D000077212:Ropivacaine; D013569:Synapses / Q000187:drug effects* / Q000502:physiology; D009435:Synaptic Transmission / Q000187:drug effects* / Q000502:physiology
chemical_list: D000577:Amides; D000779:Anesthetics, Local; D000077212:Ropivacaine; D000077554:Levobupivacaine; D000109:Acetylcholine; D002045:Bupivacaine