Potentiating effect of Bay K 8644 on agonist-induced ileal contractions

The effects of Bay K 8644 on agonist-induced ileal contractions were investigated. Histamine, serotonin and a acetylcholine (10(-8)-10(-4) M) produced a dose-dependent contraction. Maximum contraction was obtained by 10(-5) M serotonin. Its value was 1076 mg. Bay K 8644 (10(-6) M) increased the potency of histamine and serotonin-induced ileal contractions, but acetylcholine induced responses were not increased. All responses of agonists were inhibited by nifedipine (10(-6) M). This inhibition was decreased with increasing acetylcholine concentrations. These results suggest that histamine and serotonin induced/mediated contractions in guinea-pig ileum are independent of calcium influx through voltage operated channels.