Dietary tryptophan depletion alters the faecal bacterial community structure of compulsive drinker rats in schedule-induced polydipsia

• Published in: Physiology & behavior Vol. 233; p. 113356
• Main Authors: Merchán, A., Pérez-Fernández, C., López, M.J., Moreno, J., Moreno, M., Sánchez-Santed, F., Flores, P.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.05.2021
• Subjects: bacterial communities; behavior; Brain-derived neurotrophic factor; Chronic tryptophan depletion; community structure; Compulsivity; diet; digestive system; drug abuse; gel electrophoresis; Gut microbiota; intestinal microorganisms; metabolism; obsessive-compulsive disorder; PCR-DGGE; Schedule-induced polydipsia; schizophrenia; serotonin; species; tryptophan; Compulsivity; Gut microbiota; PCR-DGGE; Brain-derived neurotrophic factor; Chronic tryptophan depletion; Schedule-induced polydipsia
• ISSN: 0031-9384; 1873-507X; 1873-507X
• DOI: 10.1016/j.physbeh.2021.113356

•High drinker (HD) rats showed lower bacterial diversity than Low drinkers (LD).•Chronic dietary TRP depletion reduced bacterial evenness in HD rats.•TRP-depleted HD rats showed a highly functionally organized bacterial community.•Chronic dietary TRP depletion effectively reduced peripheral plasma 5-HT levels.•Chronic dietary TRP depletion did not alter peripheral plasma BDNF levels. Compulsive behaviour, present in different psychiatric disorders such as obsessive-compulsive disorder, schizophrenia and drug abuse, is associated with altered levels of serotonin (5-hydroxytryptamine, 5-HT). The gut microbiota regulates tryptophan (TRP) metabolism and may affect global 5-H synthesis in the enteric and central nervous systems, suggesting a possible involvement of gut microbiota in compulsive spectrum disorders. The present study investigated whether chronic TRP depletion by diet alters the faecal bacterial community profiles of compulsive versus non-compulsive rats in schedule-induced polydipsia (SIP). Peripheral plasma 5-HT and brain-derived neurotrophic factor (BDNF) levels were evaluated. Wistar rats were selected as High Drinkers (HD) or Low Drinkers (LD) according to their SIP behaviour and were fed for 14 days with either a TRP-free diet (T-) or a TRP-supplemented diet (T+). The faecal bacterial community structure was investigated with 16S rRNA gene-targeted denaturing gradient gel electrophoresis (DGGE) fingerprinting analysis. Compulsive HD rats showed a lower bacterial diversity than LD rats, irrespectively of the diet. The TRP-depleted HD rats, the only group increasing compulsive licking in SIP, showed a reduction of bacterial evenness and a highly functionally organized community compared with the other groups, indicating that this bacterial community is more fragile to external changes due to the dominance of a low number of species. The chronic TRP depletion by diet effectively reduced peripheral plasma 5-HT levels in both HD and LD rats, while plasma BDNF levels were not altered. These results highlight the possible implication of reduced microbial diversity in compulsive behaviour and the involvement of the serotonergic system in modulating the gut brain-axis in compulsive spectrum disorders.