Neonatal treatment of animals with monosodium glutamate (MSG) induces lesions of the arcuate, paraventricular and ventromedian nuclei of the hypothalamus. The aim of the study was to investigate the effect of MSG on the spleen of rats. Damage to these structures leads to functional disruption in the hypothalamic-pituitary-adrenocortical (HPA) axis. White Wister rats were used. The experimental group comprised 10 rats that underwent subcutaneous treatment with MSG (4 mg MSG per g/b.w.) on the 2nd, 4th, 6th, 8th, and 10th day of postnatal life. The control group consisted of 10 animals, as well. Four months after the treatment with MSG, the animals were sacrificed. Paraffin sections of the spleen tissue were stained using HE method. Macroscopically, the experimental animals displayed the atrophy of the spleen. Pathohistological changes in the spleen manifested as the atrophy of the while pulp. Germinate centers were missing. Follicles with preserved germinate centers were rare. In the red pulp of the spleen, there were morphologic elements of chronic delay, abundance of hemosiderophages and cell elements of hematopoiesis, especially megakaryocytes.