Introduction. Zolpidem can affect the developing embryo via the activating of the GABA A receptors. One of the important organs that expressed this receptors is fetal brain. However it is used now as a sedative even by the pregnant women. So its effect on embryo is questioned here. Materials and Methods. Female pregnant rats were randomly divided into 4 groups. Control with saline injection intra peritoneal (i.p); Treated with 5, 10, 20 mg/kg, i.p. injection of zolpidem. Zolpidem was injected at 1st post mating day. On 18th day of pregnancy, fetuses were excluded and processed for anatomical characters such as body weight, body size and head size and the end data was analyzed. Results. Our morphometric results show a significant decrease in the body weight, body size and size of the head of embryo related to the dosage. Conclusion. GABA A receptors are expressed during development of rat brain nervous system and have multiple roles in development of mammalian nervous system. zolpidem has agonistic effect on this receptors. Based on this fact, zolpidem causes disorder function of this receptor and then in some disorders in the developing fetal brain. As a result of this, there will be some malformation in the rat embryo.

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