MEASUREMENT OF ACETYLCHOLINE RELEASED FROM RABBIT DETRUSOR SMOOTH-MUSCLE USING HPLC WITH ELECTROCHEMICAL DETECTION COUPLED WITH MICRODIALYSIS PROCEDURE

We measured the amount of acetylcholine (ACh) released from rabbit det rusor smooth muscles induced by electrical field stimulation (EFS) usi ng microdialysis procedure. The dialysis probe was inserted through th e detrusor muscle strip and was continuously perfused with a Ringer so lution containing physostigmine sulfate, at a rate of 2 mu l/min. The strip was suspended in an organ bath filled with the modified Krebs-He nseleit solution and then EFS was delivered. The isometric force was r ecorded and monitored in each muscle preparation. The dialysates were collected every 10 min. ACh was determined by a high performance liqui d chromatography with electro-chemical detection. The contraction of t he muscle strip and ACh release induced by EFS were increased in a fre quency and duration dependent manner. There were some differences betw een frequency response curves of contraction and frequency dependent A Ch release. In the contractile response, the maximum contractions were observed at lower frequencies, while ACh releases reached the maximum at higher frequencies. There was a significant, but not simple correl ation between EFS-induced contraction and ACh release. The results sug gest that this new method is useful to investigate the ACh release fro m rabbit detrusor smooth muscles, and that other neurotransmitters tha n ACh possibly contribute to EFS-induced contraction. (C) 1998 Elsevie r Science Inc.