[The reaction of the chick embryo amnion to indolamines]

Abstract

Studies have been made of the effect of serotonin and tryptamine on contractile activity of nerve-free smooth muscle strip from the amnion of 7-19-day chick embryos. It was shown that stimulatory effect of indolamines depends on the age of embryos. Within 7-9 days of incubation, there was a delay in the onset of the response, the sensitivity being rather low (threshold dose for serotonin-5 microM); prolonged washing before each application of the drugs was usually necessary. At the 13-15th day, the reaction-becomes rather quick, being easily abolished by washing procedure; the sensitivity and the level of maximum reaction increase (for serotonin, mean Kd and Pmax values were equal to 0.3 microM and 62.2 mg/mg tissue respectively). Developmental changes in responses to tryptamine are similar to those described for serotonin. The effectiveness of serotonin at the 7-9th day of incubation is significantly lower than that of Ach, whereas at the 13-15th day the value of Kd is similar to that for Ach, Pmax being often higher than for the latter. The data obtained are discussed in relation to proliferation changes in amniotic tissue.