Reduction of Neurogenesis with Social Isolation Decreases Pain Sensitivity in Tail Flick Test in Male Rats

Introduction: Pain is a complex phenomenon and in many diseases is the cardinal manifestation. In many of them, the source of pain is obscure and in turn curing pain also becomes difficult. Finding a new regulatory mechanism for pain perception and processing such as alternation of neurogenesis may establish a new treatment. Methods and Materials: In this study, 32 male Sprague-Dawley rats were randomly divided into four groups: social, isolated, morphine-treated socialized (MTS) and morphine-treated isolated (MTI). After injection of BrdU for 14 days (50 mg/kg/rat/day/i.p) and morphine for seven days from day 8 (3 mg/kg/rat/day/i.p), rats were performed tail flick test and then sacrificed. Brains were prepared for assessing neurogenesis and serums were collected for assessing glutathione. Results: In tail flick test isolated and morphine-treated isolated rats had decreased sensitivity to pain stimuli compared to social and morphine-treated socialized rats, respectively. In assessing neurogenesis, isolated and morphinetreated isolated rats had reduced numbers of newly generated neurons compared to social and morphine-treated socialized rats, respectively. Glutathione in serum in isolated and morphine-treated isolated rats increased compared to social and morphine-treated socialized rats, respectively. Conclusion: Reduction of neurogenesis was associated with reduced pain sensitivity in isolated groups. So, isolation may alleviate pain and reduce pain threshold and sensitivity.