Abstract
Environmental enrichment is a popular strategy to enhance motor and cognitive performance and to counteract the effects of various harmful stimuli. The protective effects of enriched environment have been shown in traumatic, ischemic and toxic nervous system lesions. Monosodium glutamate (MSG) is a commonly used taste enhancer causing excitotoxic effects when given in newborn animals. We have previously demonstrated that MSG leads to a delay in neurobehavioral development, as shown by the delayed appearance of neurological reflexes and maturation of motor coordination. In the present study we aimed at investigating whether environmental enrichment is able to decrease the neurobehavioral delay caused by neonatal MSG treatment. Newborn pups were treated with MSG subcutaneously on postnatal days 1, 5 and 9. For environmental enrichment, we placed rats in larger cages, supplemented with different toys that were altered daily. Normal control and enriched control rats received saline treatment only. Physical parameters such as weight, day of eye opening, incisor eruption and ear unfolding were recorded. Animals were observed for appearance of reflexes such as negative geotaxis, righting reflexes, fore- and hindlimb grasp, fore- and hindlimb placing, sensory reflexes and gait. In cases of negative geotaxis, surface righting and gait, the time to perform the reflex was also recorded daily. For examining motor coordination, we performed grid walking, footfault, rope suspension, rota-rod, inclined board and walk initiation tests. We found that enriched environment alone did not lead to marked alterations in the course of development. On the other hand, MSG treatment caused a slight delay in reflex development and a pronounced delay in weight gain and motor coordination maturation. This delay in most signs and tests could be reversed by enriched environment: MSG-treated pups kept under enriched conditions showed no weight retardation, no reflex delay in some signs and performed better in most coordination tests. These results show that environmental enrichment is able to decrease the neurobehavioral delay caused by neonatal excitotoxicity.
Highlights
The first description of the positive effects of environmental enrichment comes from the neuroscientist, Donald P
We have demonstrated that treating newborn rats with Monosodium glutamate (MSG) delays the development of neurological reflexes and motor coordination skills [20,21]
There was no difference in the body weight between saline and MSG-treated pups kept in enriched environment
Summary
The first description of the positive effects of environmental enrichment comes from the neuroscientist, Donald P. In his paper in 1947, he described that the animals kept as pets, i.e., under enriched environment, showed better performance in memory and learning tasks [1]. Among others, enriched environment has been shown to influence the development of the nervous system including that of the visual system [2,3,4]. It is proven that environmental factors have a major influence on the outcome of different neuronal lesions [5] and so environmental enrichment is a popular strategy to counteract central nervous system injuries. For the first time, that environmental enrichment has a protective effect in neonatal lesion of the retina [6,7]
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