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Objective Post-traumatic stress disorder (PTSD) and chronic pain often co-occur. Studies have shown an interaction between pain and PTSD. In this narrative review, we aim to support conducting comprehensive studies by describing PTSD, pain and determining whether opioidergic system, its agonist and antagonist manipulation could positively or negatively affect PTSD symptoms and concurrent pain.Methods Term searches was done in Google Scholar, Scopus, ScienceDirect, Web of Science and PubMed databases as well as hand searching in key resource journals from 1979–2019.Results There are a lot of contradictions and disputes when endogenous opioidergic system and opioidergic antagonist system are studied in PTSD patients. Exogenous morphine administration in PTSD patients can decrease the symptoms of PTSD but it doesn’t have a pain reduction effect to an acceptable level. Beta-endorphin as an endogenous opioid is effective in pain reduction in the moment of events but after minutes to hours, the endorphins withdrawal syndrome leads to exaggerated intrusive thoughts and flashbacks of PTSD, which exacerbate the pain. It has also been shown that naloxone, as an opioidergic antagonist, can reduce or increase the PTSD symptoms and its associated pain.Conclusion Data suggest different roles of opioidergic system and their antagonist in pain control and mood in PTSD. However, further investigations need to be done in order to reveal the role of endogenous opioidergic system and opioidergic antagonist system as a mediator in PTSD patients suffering from acute or chronic pain.

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.

Background: Separation of pups from their dam during the infancy not only has detrimental effects on the pups' brain but also affects dams' behavior. Postpartum stress may affect mothers' cognitive functions. In the present study, by using a 180 min/day maternal separation (MS) paradigm, we assessed anxiety-like behavior (in the elevated plus maze) and locomotor activity (in the open eld) of rat dams which experienced separation from postnatal day (PND) 1 until weaning. Since no study has ever investigated MS effects on spatial learning and memory of dams in the Morris water maze, we tried for the rst time to clarify whether such separation impairs dam's performance in the Morris water maze.Methods:We assessed dams' behavior at three time points; 24 hours, 1 week and 1 month after weaning.Therefore, the six groups consisted of control (CTRL); 24h, 1week and 1month and MS; 24h, 1week and 1month was allocated in this study.Results: Our results revealed that although MS-24h and MS-1week groups had intact locomotor activity, MS-1month group showed less locomotor activity in the open eld. Moreover, MS induced anxiety-like behavior was more pronounced in MS-1week and MS-1month dams. Spatial learning and memory was also impaired only in MS-1month dams.Conclusions: We can conclude that MS induces cognitive impairments in dam that may appear not immediately after the separation, but a few weeks after such stressful event.