{"id":"1d6b8666-1e95-52c5-b5af-0c459fbf1ee4","stable_key":"ea2f0904-ab2c-5d1e-a3d4-3f7ecdd70cd6:caf-human-a1","predicate":"occupies","statement":"Caffeine displaced 5–44% of the A1 PET ligand signal; modeled half-maximal displacement corresponded to plasma caffeine of 67 micromolar.","claim_class":"mechanistic","status":"source_derived_draft","evidence_grade":"ungraded","direction":"context_dependent","is_public":true,"mechanism_event_id":"1cf9a609-ae67-5b36-98c9-42d9613fe1c3","mechanism_event_label":"Caffeine reached and occupied adenosine receptors in the human brain.","subject":{"id":"ef028472-7c33-583d-b52e-40676004d370","slug":"caffeine","display_name":"Caffeine","entity_type_key":"small_molecule"},"object":{"id":"176c7b0e-dd39-57ca-b4ec-a551358b5079","slug":"adora1","display_name":"Human adenosine A1 receptor / ADORA1","entity_type_key":"protein"},"evidence_count":1,"mechanism_event":{"id":"1cf9a609-ae67-5b36-98c9-42d9613fe1c3","stable_key":"ea2f0904-ab2c-5d1e-a3d4-3f7ecdd70cd6:caf-human-a1-event","event_type":"observed_relationship","label":"Caffeine reached and occupied adenosine receptors in the human brain.","description":"Caffeine displaced 5–44% of the A1 PET ligand signal; modeled half-maximal displacement corresponded to plasma caffeine of 67 micromolar.","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":"176c7b0e-dd39-57ca-b4ec-a551358b5079","slug":"adora1","display_name":"Human adenosine A1 receptor / ADORA1","entity_type_key":"protein"},"role":"target","stoichiometry":null,"state_label":"","sequence_order":1,"notes":""},{"entity":{"id":"52389a5d-d5fb-5fc5-a104-fced0188af8c","slug":"brain-a1-receptor-occupancy","display_name":"Human cerebral A1 receptor occupancy","entity_type_key":"cellular_process"},"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":"15 adults; 0.5–4.3 mg/kg intravenous caffeine after at least 36 hours abstinence; one vehicle subject.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"limitations","value_text":"PET occupancy does not establish that A1 alone mediates wakefulness or a universal oral-dose threshold.","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 reached and occupied adenosine receptors in the human brain.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"primary_references","value_text":"Caffeine occupancy of human cerebral A1 adenosine receptors: in vivo quantification with 18F-CPFPX and PET. · 2012 · https://pubmed.ncbi.nlm.nih.gov/22966134/ · DOI 10.2967/jnumed.112.105114","comparator":null,"unit":null,"notes":"","entity":null}],"evidence":[{"id":"1857bc61-9de1-50a3-8748-fbe8ec21f4c4","evidence_kind":"source_excerpt","locator":"Lines 20-26","start_line":20,"end_line":26,"excerpt":"## caf-human-a1\nCaffeine reached and occupied adenosine receptors in the human brain.\nCaffeine displaced 5–44% of the A1 PET ligand signal; modeled half-maximal displacement corresponded to plasma caffeine of 67 micromolar.\nModel: 15 adults; 0.5–4.3 mg/kg intravenous caffeine after at least 36 hours abstinence; one vehicle subject.\nLimitations: PET occupancy does not establish that A1 alone mediates wakefulness or a universal oral-dose threshold.\nEvidence access: Primary abstract\nCaffeine occupancy of human cerebral A1 adenosine receptors: in vivo quantification with 18F-CPFPX and PET. · 2012 · https://pubmed.ncbi.nlm.nih.gov/22966134/ · DOI 10.2967/jnumed.112.105114","model_system":"15 adults; 0.5–4.3 mg/kg intravenous caffeine after at least 36 hours abstinence; one vehicle subject.","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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