Various effects were shown to act alter the proceeding of histogenetic processes in the embryonic neural tissue. Studies in mice revealed that, depending on the embryogenesis stage when a lack of serotonin occurred, the lack of this monoamine entails either death of the embryo or a teratogenic effect, or underdevelopment of brain structures. In the rat model of a shorten hypoxia, a disorder of neural tissue histogenesis in early stages of development, was found, as well as a reduction of its sensitivity to lack of oxygen by the end of embryogenesis.