{"title":"Liver tryptophan 2,3-dioxygenase: a determinant of anxiety-like behaviour - studies with chronic nicotine administration in rats.","authors":"Samina Bano, Humaira Sharif, Faiza Sajid, Sumaiya Binte Hamid, Abdulla A-B Badawy","doi":"10.1097/FBP.0000000000000736","DOIUrl":null,"url":null,"abstract":"<p><p>Deletion of the tryptophan 2,3-dioxygenase ( TDO2 ) gene induces an anxiolytic-like behaviour in mice and TDO inhibition by allopurinol elicits an antidepressant-like effect in rats exposed to restraint stress. Chronic nicotine administration inhibits TDO activity, enhances brain serotonin synthesis and exerts anxiolytic- and antidepressant-like effects in rodent models. There is a strong association between anxiety, depression and tobacco use, which is stronger in women than in men. The present study aimed to examine the relationship between behavioural measures of anxiety and depression with liver TDO activity, brain tryptophan concentration and serotonin synthesis in rats treated chronically with nicotine. Behavioural measures included the elevated plus maze (EPM), open field (OFT) and forced swim (FST) tests. Biochemical measures included TDO activity, serum corticosterone and brain Trp, 5-HT and 5-HIAA concentrations. Anxiolytic-like and antidepressant-like effects of chronic nicotine were confirmed in association with TDO inhibition and elevation of brain Trp and 5-HT. Sex differences in behaviour were independent of the biochemical changes. At baseline, female rats performed better than males in OFT and FST. Nicotine was less anxiolytic in females in the open arm test. Nicotine treatment did not elicit different responses between sexes in the FST. Our findings support the notion that liver TDO activity exhibits a strong association with behavioural measures of anxiety and depression in experimental models, but provide little evidence for sex differences in behavioural response to nicotine. The TDO-anxiety link may be underpinned by kynurenine metabolites as well as serotonin.</p>","PeriodicalId":8832,"journal":{"name":"Behavioural Pharmacology","volume":null,"pages":null},"PeriodicalIF":1.6000,"publicationDate":"2023-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Behavioural Pharmacology","FirstCategoryId":"102","ListUrlMain":"https://doi.org/10.1097/FBP.0000000000000736","RegionNum":4,"RegionCategory":"心理学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q3","JCRName":"BEHAVIORAL SCIENCES","Score":null,"Total":0}
引用次数: 0
Abstract
Deletion of the tryptophan 2,3-dioxygenase ( TDO2 ) gene induces an anxiolytic-like behaviour in mice and TDO inhibition by allopurinol elicits an antidepressant-like effect in rats exposed to restraint stress. Chronic nicotine administration inhibits TDO activity, enhances brain serotonin synthesis and exerts anxiolytic- and antidepressant-like effects in rodent models. There is a strong association between anxiety, depression and tobacco use, which is stronger in women than in men. The present study aimed to examine the relationship between behavioural measures of anxiety and depression with liver TDO activity, brain tryptophan concentration and serotonin synthesis in rats treated chronically with nicotine. Behavioural measures included the elevated plus maze (EPM), open field (OFT) and forced swim (FST) tests. Biochemical measures included TDO activity, serum corticosterone and brain Trp, 5-HT and 5-HIAA concentrations. Anxiolytic-like and antidepressant-like effects of chronic nicotine were confirmed in association with TDO inhibition and elevation of brain Trp and 5-HT. Sex differences in behaviour were independent of the biochemical changes. At baseline, female rats performed better than males in OFT and FST. Nicotine was less anxiolytic in females in the open arm test. Nicotine treatment did not elicit different responses between sexes in the FST. Our findings support the notion that liver TDO activity exhibits a strong association with behavioural measures of anxiety and depression in experimental models, but provide little evidence for sex differences in behavioural response to nicotine. The TDO-anxiety link may be underpinned by kynurenine metabolites as well as serotonin.
期刊介绍：
Behavioural Pharmacology accepts original full and short research reports in diverse areas ranging from ethopharmacology to the pharmacology of schedule-controlled operant behaviour, provided that their primary focus is behavioural. Suitable topics include drug, chemical and hormonal effects on behaviour, the neurochemical mechanisms under-lying behaviour, and behavioural methods for the study of drug action. Both animal and human studies are welcome; however, studies reporting neurochemical data should have a predominantly behavioural focus, and human studies should not consist exclusively of clinical trials or case reports. Preference is given to studies that demonstrate and develop the potential of behavioural methods, and to papers reporting findings of direct relevance to clinical problems. Papers making a significant theoretical contribution are particularly welcome and, where possible and merited, space is made available for authors to explore fully the theoretical implications of their findings. Reviews of an area of the literature or at an appropriate stage in the development of an author’s own work are welcome. Commentaries in areas of current interest are also considered for publication, as are Reviews and Commentaries in areas outside behavioural pharmacology, but of importance and interest to behavioural pharmacologists. Behavioural Pharmacology publishes frequent Special Issues on current hot topics. The editors welcome correspondence about whether a paper in preparation might be suitable for inclusion in a Special Issue.
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