ANTAGONISTIC EFFECTS OF TRIFLUOPERAZINE, IMIPRAMINE, AND CHLORPROMAZINE AGAINST ACETYLCHOLINE-INDUCED CONTRACTIONS IN ISOLATED RAT UTERUS

AIM: To examine the effects and affinity of some phenothizines (triflu operazine, Tri and chlorpromazine, Chi) and antidepressant (imipramine , Imi) drugs on acetylcholine (ACh)-induced uterine contraction. METHO DS: Isotonic contractions of rat uterine strips were recorded. ACh was administrated to induce maximal contraction before exchange of nutrie nt solution. ACh was added 5 min after the testing drugs. The nutrient solution was exchanged 4 times after each agonist (ACh or other agent s) to produce maximal contraction. RESULTS: Atropine (Atr, 0.029 - 2.9 mu mol . L(-1)), 4-DAMP (3.6 - 360 nmol . L(-1)), pirenzepine (Pir, 0 .23 - 23.5 mu mol . L(-1)), and AF-DX 116 (0.7 - 35.6 mu mol . L(-1)) competitively antagonized the muscular uterine contraction induced by ACh (0.068-36068 mu mol . L(-1)). The Schild plot was linear (r = 1.00 ). The pK(B) and slopes values (95 % confidence limits) were 9.28 +/- 0.12 and 1.00 +/- 0.10 to Atr, 9.06 +/- 0.10 and 1.10 +/- 0.08 to 4-DA MP, 7.03 +/- 0.15 and 0.99 +/- 0.12 to Pir, and 5.60 +/- 0.08 and 1.00 +/- 0.19 to AF-DX 116. Tri 0.01 - 2 mu mol . L(-1) (pK(B) = 8.39 +/- 0.04) and Imi 94 - 940 nmol . L(-1) (pK(B) = 7.21 +/- 0.10) produced a lso a competitive antagonism of the muscular uterine contraction induc ed by ACh (r = 1.00), but the slope was only 0.60 +/- 0.03 to Tri or 0 .83 +/- 0.16 to Imi. Chl 2.8 - 5.6 mu mol . L(-1) produced a weak anta gonism on amplitude of muscular contraction induced by the cholinomime tic. CONCLUSION: The muscarinic receptors on uterus behaved as M(3) su btype. Tri and Imi, but: not Chl, were competitive antagonist of musca rinic receptors of uterus. Imi behaved a simple competitive antagonist at a single site on myometrium, but Tri was not a simple competitive agent at a single site.