Synergistic Effects of Social Isolation and Morphine Addiction on Reduced Neurogenesis and BDNF Levels and the Resultant Deficits in Cognition and Emotional State in Male Rats

Introduction: Addiction to drugs of abuse is a devastating condition which results in deterioration of brain function. On the other hand, social isolation also produces cognitive deficits such as learning and memory impairment. This study was designed to evaluate the potential negative synergistic effects of social isolation and morphine addiction on brain functions. Methods and Material: One hundred and two Sprague-Dawley rats were randomly divided into four groups for assessing neurogenesis and behaviour: group-housed, isolated, morphine-treated group-housed and morphine-treated isolated groups. Morphine- treated animals received BrdU (50 mg/kg; i.p.) and Morphine (0.75 mg/rat; i.p.) for 14 consecutive days, whereas, control rats received BrdU (50 mg/kg; i.p.) only. At the end of the study, Morris water maze and elevated plus maze tasks were performed to assess spatial working memory and anxiety levels, respectively. Furthermore, neurogenesis and BDNF levels were studied. Results: Reference and working memory was markedly impaired in isolated and morphine-treated isolated rats as compared to group-housed rats and morphine-treated group-housed rats, respectively. Neurogenesis and BDNF levels were reduced in isolated and morphine-treated isolated rats as compared to group-housed rats and morphine-treated group-housed rats, respectively. Furthermore, rats in both isolated groups demonstrated low anxiety levels when compared to group housed groups. Conclusion: Isolation during addiction imparts devastating effects on brain. Thus, socialization of addicts can minimize addiction - induce cognitive deficits and improve neurogenesis.