{"doi":"10.1111/j.1460-9568.2005.04264.x","title":"Tissue‐specific expression of tryptophan hydroxylase mRNAs in the rat midbrain: anatomical evidence and daily profiles","abstract":"<jats:title>Abstract</jats:title><jats:p>Serotonin (5‐HT) is involved in both photic and non‐photic synchronization of the mammalian biological clock located in the suprachiasmatic nuclei (SCN). We have previously demonstrated that tryptophan hydroxylase protein (TPH), the rate‐limiting enzyme of 5‐HT synthesis, shows circadian rhythmicity in the pathways projecting from the raphe nuclei to the intergeniculate leaflets of the thalamus on one hand, and to the SCN on the other hand. In this study, we investigate whether the circadian rhythmicity in TPH protein could result from the rhythmic expression of <jats:italic>tph</jats:italic> gene in the raphe nuclei. We thus cloned specific <jats:italic>tph1</jats:italic> and <jats:italic>tph2</jats:italic> partial cDNAs and assessed the daily profiles of TPH mRNA levels by <jats:italic>in situ</jats:italic> hybridization in the rat raphe nuclei. Our results demonstrate that: (i) <jats:italic>tph</jats:italic>2 gene is exclusively expressed in the raphe nuclei, whereas <jats:italic>tph1</jats:italic> gene is expressed in the pineal gland; (ii) under light–dark cycle (LD), TPH2 mRNA levels present daily variation within both median and dorsal raphe nuclei; (iii) under constant darkness TPH2 mRNA levels in both nuclei exhibit the same variation reported under LD cycle.</jats:p><jats:p>These data show that the circadian 5‐HT synthesis within the serotonergic neurons projecting to the circadian system might be explained by the rhythmic transcription of the <jats:italic>tph2</jats:italic> gene in raphe nuclei. Taking our result with previous data into consideration, we further suggest that 5‐HT synthesis and release within the circadian system could be directly or indirectly under the control of the SCN.</jats:p>","journal":"European Journal of Neuroscience","year":2005,"id":34537,"datarank":4.763593129888057,"base_score":4.836281906951478,"endowment":4.836281906951478,"self_citation_contribution":0.7254422860427218,"citation_network_contribution":4.038150843845335,"self_endowment_contribution":0.7254422860427218,"citer_contribution":4.038150843845335,"corpus_percentile":null,"corpus_rank":null,"citation_count":125,"citer_count":115,"citers_with_citation_signal":101,"citers_with_endowment":101,"datacite_reuse_total":0,"is_dataset":false,"is_dataset_confidence":null,"is_oa":false,"file_count":0,"downloads":0,"has_version_chain":false,"published_date":null,"fair_score":null,"fair_percentile":null,"algorithm_id":"datarank_citation_only_1hop_v6","ranking_scope":"data_only","authors":[{"id":178727,"name":"Hugues Dardente","orcid":null,"position":1,"is_corresponding":false},{"id":178729,"name":"Paul Pevet","orcid":null,"position":2,"is_corresponding":false},{"id":178731,"name":"Sylvie Raison","orcid":null,"position":3,"is_corresponding":false},{"id":178724,"name":"Zeina S. Malek","orcid":null,"position":0,"is_corresponding":false}],"reference_count":0,"raw_metadata":{"has_enrichment":true,"base_score":4.836281906951478,"endowment":4.836281906951478,"datacite_reuse_total":0,"file_count":0,"downloads":0,"views":0,"has_version_chain":false,"is_dataset":false,"is_oa":false,"pmid":"16115212","pmcid":null,"openalex_id":"https://openalex.org/W2096221719","authors":[],"funders":[],"total_grants":0,"fwci":1.689,"citation_percentile":0.8322968,"influential_citations":4,"citation_trend":[{"year":2012,"count":6},{"year":2013,"count":2},{"year":2014,"count":4},{"year":2015,"count":7},{"year":2016,"count":3},{"year":2017,"count":5},{"year":2018,"count":4},{"year":2019,"count":4},{"year":2020,"count":5},{"year":2021,"count":3},{"year":2022,"count":13},{"year":2023,"count":9},{"year":2024,"count":10},{"year":2025,"count":1},{"year":2026,"count":4}],"oa_status":"closed","license":"http://onlinelibrary.wiley.com/termsAndConditions#vor","oa_locations":[{"url":"https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fj.1460-9568.2005.04264.x","host_type":"publisher"},{"url":"https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1460-9568.2005.04264.x","host_type":"publisher"},{"url":"https://doi.org/10.1111/j.1460-9568.2005.04264.x","host_type":"journal"},{"url":"https://pubmed.ncbi.nlm.nih.gov/16115212","host_type":"repository"},{"url":"https://hal.science/hal-00093864","host_type":"repository"}],"fields_of_study":["Circadian rhythm and melatonin","Neuroendocrine regulation and behavior","Sleep and Wakefulness Research","Biology","Medicine"],"mesh_terms":["Animals","Behavior, Animal","Circadian Rhythm","Cloning, Molecular","Gene Expression Regulation","Immunohistochemistry","Male","Raphe Nuclei","RNA, Messenger","Serotonin","Time Factors","Tryptophan Hydroxylase","Rats, Wistar","In Situ Hybridization","Rats"],"keywords":["TPH2","Tryptophan hydroxylase","Dorsal raphe nucleus","Raphe nuclei","Suprachiasmatic nucleus","Biology","Circadian rhythm","Serotonergic","Serotonin","Raphe","Endocrinology","Internal medicine","Genetics"],"sdg_mappings":[],"linked_datasets":[],"clinical_trials":[],"software_tools":[],"database_accessions":[],"source":"live","citation_network_status":"fetched"},"created_at":"2026-06-09T18:59:07.087629Z","pmid":null,"pmcid":null,"fwci":null,"citation_percentile":null,"influential_citations":0,"oa_status":null,"license":null,"views":0,"total_file_size_bytes":0,"version_count":0,"fair_f":null,"fair_a":null,"fair_i":null,"fair_r":null,"fair_zscore":null,"fair_rationale":null,"fair_model":null,"fair_agent_version":null,"fair_fulltext_source":null,"fair_has_llm":null,"fair_computed_at":null,"clinical_trials":[],"software_tools":[],"db_accessions":[],"linked_datasets":[],"topics":[]}