Environmental enrichment and pain sensitivity; a study in maternally separated rats.

Rodents are highly dependent on maternal care after birth. Maternal separation (MS) is an animal model for studying neglect and abuse. Depriving the pup of such care renders the animal with Hypothalamic-Pituitary-adrenal (HPA) dysfunction and these animals are more susceptible to anxiety and stress as well as poor cognition. These effects are due to abnormal brain development in these animals. We have tried to investigate how maternal separation can affect pain sensation and whether a non-pharmacological intervention such as enriched environment (EE) can restore an abnormal pain sensation. Animals were put into four groups MS, control (CTRL) and MS + EE and CTRL + EE groups that underwent EE after weaning until adulthood. These groups were tested for pain sensitivity with hot plate and tail flick for sensory pain and formalin for affect pain. The results showed that MS rats are more sensitive to pain in the hot plate test and formalin test, however, no significant difference was seen between groups for tail flick test. When MS rats experience EE their pain sensitivity is restored at the behavioral level. Further research is required to see how EE restores pain sensation in MS rats.