Commercial cow’s milk supplementation affects synaptic proteins and behavioral patterns in mice

Abstract Cow's milk, a bioactive cocktail with essential nutritional factors widely consumed during early childhood development, has been associated with allergic responses, immune cell activation and typical autistic behaviors in children. In order to investigate whether cow’s milk consumption regulates autistic behavior, we used BALB/c mouse as experimental model because they were described by low sociability, significant stereotypes and restrict interest features. The major aims were focused in to investigate whether milk supplementation triggers mechanisms that interfere with behavioral patterns in genetically predisposed mice. Animals received orally commercial cow’s milk or water (controls), three times per day for one week. Milk consumption affected the distribution of Drebrin and Shank-3, both post-synaptic proteins, in the cerebral cortex. By immunohistochemistry and histomorphometry, we found that Drebrin+ and Shank-3+ cells significantly decreased in the cortex. No significant changes were observed in cortical cells expressing Synapotophysin (pre-synaptic protein). The milk intake enhanced the number of Iba-1+ cells in the cortical brain and cerebellum, and the number of Purkinje cells expressing nitric oxide synthase 2 (NOS2), suggesting neuroinflammatory and oxidative stress signals, respectively. These histological changes were correlated with disturbances on behavioral patterns after milk consumption. Mice supplemented with milk amplified pre-existing atypic movements, including significant stereotypies, restrict interest and low sociability. In addition, Global Motility Test revealed that milk-treated mice moved in repeated paths on the border of open field arena, exploring 40% less its perimeter than control group. On the other hand, milk consumption did not interfere with velocity, total distance explored, motor functions, fine motor skills or sensibility in hind limb paws of BALB/c mice. In conclusion, we suggest that milk consumption in genetically predisposed mice amplificated atypic behaviors involving mechanisms linked to synapse, neuroinflammation and oxidative stress regulation.