It is revealed that glutaminic acid (GA) synthesis by direct reductive amination proves to be the most rapid in the mitochondria of the outer geniculate body (OGB) from the 1st till the 45th day of the postnatal development, and beginning from the 45th day till the 3-month age in visual cortex (field 17) (VC) and bigeminal bodies (BB). It is stated that GA synthesis by transamination in the mitochondria of VC, OGB, and BB proceeds less intensively than by a direct reductive amination at the early stage of postnatal development, being more rapid during the period from the 12-16th till the 45th day of postnatal development. Unlike GA synthesis in the mitochondria of the studied visual analyzer structures of canine brain AsA synthesis is more rapid in transamination reaction at the early stage of postnatal development. The high level of AsA synthesis was observed on the day when the puppies' eyes began to see clearly. The level of AsA synthesis by reductive amination and transamination in the mitochondria of VC, BB, and OGB at the early stage of postnatal development is lower than that of GA synthesis.