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[The reaction of the chick embryo amnion to indolamines]
Insights
Serotonin and tryptamine affect chick embryo amnion muscle differently based on embryonic age. Sensitivity and response speed increase significantly with development, impacting smooth muscle contractile activity.
Area of Science:
- Developmental biology
- Pharmacology
- Physiology
Context:
- Investigating the contractile properties of nerve-free smooth muscle in chick embryo amnions.
- Examining the influence of indolamines, specifically serotonin and tryptamine, on smooth muscle activity.
Purpose:
- To determine how embryonic age affects the response of chick embryo amnion smooth muscle to serotonin and tryptamine.
- To characterize the developmental changes in sensitivity and contractile response to these neurotransmitters.
Summary:
- The stimulatory effects of serotonin and tryptamine on chick embryo amnion smooth muscle are age-dependent.
- Early in development (7-9 days), responses are slow and require higher concentrations, while later (13-15 days), responses are rapid, more sensitive, and potent.
- Serotonin's effectiveness increases with embryonic development, becoming comparable or superior to acetylcholine by day 13-15.
Impact:
- Provides insights into the developmental neuropharmacology of smooth muscle.
- Highlights the role of indolamines in avian embryonic development.
- Suggests a correlation between observed pharmacological changes and amniotic tissue proliferation.
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.