Effect of retinoic acid on neural tube development in chick embryo

retinoic acid is one of the derivatives of vitamin A.it is used for treatment of dermatitis,but it has different teratogenic effects on developing organs depending on the different stages of embryonic life.neural  tube is made of two different parts:primary neural tube originated from embryo germinal layer and and secondary neural tube originated from tail bud.the persent study was designed to compare the effects of different doses of retinoic acid on primary and secondary neural tube development in the stages of 11-12 humburger & hamilton.in order to do this,254 white leghorn eggs were divided to six groups for futher direct studies.four of the groups were injection with either of:0.3,0.5,0.7, and 1 microgram solution of retinoic acid in 2 microliter of dimethyl sulfoxide,the fifth group was injected with only dimethylsulfoxide,and no injection was made to the last group(sham).forty eight hours later embryos were removed and studied both microscopically and macroscopically.the results showed that,retinoic acid with the dose of 0.5 microgram caused the primary neural tube to be left open and produced accessory neural tube with comparison to the control group(p<0.05).this study suggests that one of the teratogenic effects of retinoic acid in chick embryo is abnormality in the nervous system presented as open primary neural tube or producation of accessory neural tube.