{"id":"747302d9-d419-5a24-892b-3c3dfc6ba03d","stable_key":"ea2f0904-ab2c-5d1e-a3d4-3f7ecdd70cd6:caf-dopamine-pet","predicate":"increases","statement":"Caffeine 300 mg increased D2/D3 PET availability in putamen and ventral striatum, but not caudate, in 20 healthy participants.","claim_class":"observational","status":"source_derived_draft","evidence_grade":"ungraded","direction":"positive","is_public":true,"mechanism_event_id":"feea8500-6dd7-5e56-940f-8ba301f2da51","mechanism_event_label":"Caffeine changed a dopamine-receptor measurement in selected brain regions.","subject":{"id":"ef028472-7c33-583d-b52e-40676004d370","slug":"caffeine","display_name":"Caffeine","entity_type_key":"small_molecule"},"object":{"id":"13a22e3c-99ba-57b1-ace1-68247c6af058","slug":"striatal-d2-d3-pet-availability","display_name":"Striatal dopamine D2/D3 receptor availability measured by PET","entity_type_key":"cellular_process"},"evidence_count":1,"mechanism_event":{"id":"feea8500-6dd7-5e56-940f-8ba301f2da51","stable_key":"ea2f0904-ab2c-5d1e-a3d4-3f7ecdd70cd6:caf-dopamine-pet-event","event_type":"observed_relationship","label":"Caffeine changed a dopamine-receptor measurement in selected brain regions.","description":"Caffeine 300 mg increased D2/D3 PET availability in putamen and ventral striatum, but not caudate, in 20 healthy participants.","status":"provisional","compartment":null,"participants":[{"entity":{"id":"ef028472-7c33-583d-b52e-40676004d370","slug":"caffeine","display_name":"Caffeine","entity_type_key":"small_molecule"},"role":"subject","stoichiometry":null,"state_label":"","sequence_order":0,"notes":""},{"entity":{"id":"13a22e3c-99ba-57b1-ace1-68247c6af058","slug":"striatal-d2-d3-pet-availability","display_name":"Striatal dopamine D2/D3 receptor availability measured by PET","entity_type_key":"cellular_process"},"role":"target","stoichiometry":null,"state_label":"","sequence_order":1,"notes":""},{"entity":{"id":"4b987ba4-81d4-56ce-8721-15aea1e528a2","slug":"dopamine-d2-d3-receptor-pool","display_name":"Human dopamine D2/D3 receptor pool in raclopride PET","entity_type_key":"protein_set"},"role":"context_participant","stoichiometry":null,"state_label":"","sequence_order":2,"notes":""}]},"contexts":[{"dimension":"evidence_access","value_text":"Primary abstract","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"experimental_model","value_text":"Human raclopride PET, caffeine versus placebo.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"limitations","value_text":"Availability can reflect receptor levels or affinity. The direction did not support a simple increase in striatal dopamine release; receptor upregulation was an interpretation.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"nutrient_topic","value_text":"Caffeine collection; salts, coffee, species and coexposure contexts retain their identities.","comparator":null,"unit":null,"notes":"","entity":{"slug":"caffeine","display_name":"Caffeine","entity_type_key":"small_molecule"}},{"dimension":"plain_language","value_text":"Caffeine changed a dopamine-receptor measurement in selected brain regions.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"primary_references","value_text":"Caffeine increases striatal dopamine D2/D3 receptor availability in the human brain. · 2015 · https://pubmed.ncbi.nlm.nih.gov/25871974/ · DOI 10.1038/tp.2015.46","comparator":null,"unit":null,"notes":"","entity":null}],"evidence":[{"id":"b6dd5578-8453-5bdd-b065-54ad7ff3db14","evidence_kind":"source_excerpt","locator":"Lines 68-74","start_line":68,"end_line":74,"excerpt":"## caf-dopamine-pet\nCaffeine changed a dopamine-receptor measurement in selected brain regions.\nCaffeine 300 mg increased D2/D3 PET availability in putamen and ventral striatum, but not caudate, in 20 healthy participants.\nModel: Human raclopride PET, caffeine versus placebo.\nLimitations: Availability can reflect receptor levels or affinity. The direction did not support a simple increase in striatal dopamine release; receptor upregulation was an interpretation.\nEvidence access: Primary abstract\nCaffeine increases striatal dopamine D2/D3 receptor availability in the human brain. · 2015 · https://pubmed.ncbi.nlm.nih.gov/25871974/ · DOI 10.1038/tp.2015.46","model_system":"Human raclopride PET, caffeine versus placebo.","directness":"reported_statement","verification_status":"source_derived_draft","notes":"Original curation paraphrase; evidence access stated with the claim.","relationship":"supports","weight":1.0,"link_notes":"","source":{"id":"40a654db-878c-5471-bc6c-88f4f52599c0","stable_key":"import-ea2f0904-ab2c-5d1e-a3d4-3f7ecdd70cd6","title":"Caffeine: receptors, metabolism, nutrient interactions, adaptation and discovery questions (2026-09-18)","document_type":"imported_text","citation_label":"AI-assisted research curation; primary-abstract references and experimental limitations individually identified. 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