{"id":"3dba7334-c380-548a-a53e-45787fbec7df","stable_key":"7de430a5-1a36-5231-b931-35cc01d8f3bf:apap-hypothermia-is-a-different-mechanism","predicate":"preserves_measured_pool","statement":"Paracetamol induced hypothermia to the same extent in cannabinoid receptor 1 and TRPV1 knockout mice as in wild-type mice and to the same extent in mice pretreated with the antagonists AM251 or SB366791 as in controls, AM404 failed to induce hypothermia at pharmacological doses, inhibition of fatty acid amide hydrolase did not prevent the development of hypothermia and paracetamol induced hypothermia in fatty acid amide hydrolase knockout mice to the same extent as in wild-type mice, so paracetamol induces hypothermia independent of cannabinoids and TRPV1 and AM404 does not mediate this response.","claim_class":"observational","status":"source_derived_draft","evidence_grade":"ungraded","direction":"neutral","is_public":true,"mechanism_event_id":"b1e97585-3b9b-5dd6-874b-4cd5ae8c53fa","mechanism_event_label":"The same knockouts that abolish the painkilling leave the temperature drop completely untouched.","subject":{"id":"e7864d65-3251-50c8-a6da-083275f96014","slug":"am404","display_name":"AM404 / N-arachidonoylphenolamine","entity_type_key":"small_molecule"},"object":{"id":"45163a52-38d5-5f0b-a87c-241166f53709","slug":"paracetamol-hypothermia","display_name":"Hypothermia induced by paracetamol below normal body temperature","entity_type_key":"cellular_process"},"evidence_count":1,"mechanism_event":{"id":"b1e97585-3b9b-5dd6-874b-4cd5ae8c53fa","stable_key":"7de430a5-1a36-5231-b931-35cc01d8f3bf:apap-hypothermia-is-a-different-mechanism-event","event_type":"observed_intervention","label":"The same knockouts that abolish the painkilling leave the temperature drop completely untouched.","description":"Paracetamol induced hypothermia to the same extent in cannabinoid receptor 1 and TRPV1 knockout mice as in wild-type mice and to the same extent in mice pretreated with the antagonists AM251 or SB366791 as in controls, AM404 failed to induce hypothermia at pharmacological doses, inhibition of fatty acid amide hydrolase did not prevent the development of hypothermia and paracetamol induced hypothermia in fatty acid amide hydrolase knockout mice to the same extent as in wild-type mice, so paracetamol induces hypothermia independent of cannabinoids and TRPV1 and AM404 does not mediate this response.","status":"provisional","compartment":null,"participants":[{"entity":{"id":"d092243c-94e9-5f03-a406-2fa245f2f4ae","slug":"cnr1","display_name":"Human cannabinoid receptor 1 / CB1 / CNR1","entity_type_key":"protein"},"role":"excluded_receptor","stoichiometry":null,"state_label":"","sequence_order":0,"notes":""},{"entity":{"id":"8e0c61d8-3930-51d5-bce2-25a5edfb797c","slug":"human-trpv1","display_name":"Human transient receptor potential vanilloid 1 / TRPV1","entity_type_key":"protein"},"role":"excluded_channel","stoichiometry":null,"state_label":"","sequence_order":1,"notes":""},{"entity":{"id":"a4a100bc-130e-5006-bad6-58103aa6da55","slug":"faah","display_name":"Fatty acid amide hydrolase / FAAH","entity_type_key":"protein"},"role":"excluded_enzyme","stoichiometry":null,"state_label":"","sequence_order":2,"notes":""},{"entity":{"id":"70ee4444-3735-5b45-a90f-fdbdf2f21096","slug":"cb1-null-mouse","display_name":"Cannabinoid receptor 1 knockout mouse genotype","entity_type_key":"protein_state"},"role":"test_genotype","stoichiometry":null,"state_label":"","sequence_order":3,"notes":""},{"entity":{"id":"c14b326b-f015-505d-b517-4897c635aa1a","slug":"trpv1-null-mouse","display_name":"TRPV1 knockout mouse genotype","entity_type_key":"protein_state"},"role":"test_genotype","stoichiometry":null,"state_label":"","sequence_order":4,"notes":""},{"entity":{"id":"514451f2-5b73-501c-a004-07c1f7895cbd","slug":"sb366791","display_name":"SB366791 TRPV1 antagonist","entity_type_key":"drug"},"role":"test_antagonist","stoichiometry":null,"state_label":"","sequence_order":5,"notes":""},{"entity":{"id":"717251de-de2d-52ab-9130-ba2dabda79a3","slug":"am251","display_name":"AM251, a cannabinoid receptor 1 antagonist","entity_type_key":"chemical_species"},"role":"test_antagonist","stoichiometry":null,"state_label":"","sequence_order":6,"notes":""},{"entity":{"id":"e7864d65-3251-50c8-a6da-083275f96014","slug":"am404","display_name":"AM404 / N-arachidonoylphenolamine","entity_type_key":"small_molecule"},"role":"subject","stoichiometry":null,"state_label":"","sequence_order":7,"notes":""},{"entity":{"id":"45163a52-38d5-5f0b-a87c-241166f53709","slug":"paracetamol-hypothermia","display_name":"Hypothermia induced by paracetamol below normal body temperature","entity_type_key":"cellular_process"},"role":"target","stoichiometry":null,"state_label":"","sequence_order":8,"notes":""}]},"contexts":[{"dimension":"evidence_span","value_text":"{\"source_cache\": \"artifacts/paracetamol-research/21628499.abstract.txt\", \"locator\": \"Indexed abstract; zero-based, end-exclusive Unicode character offsets\", \"file_sha256\": \"784e57af3594f8d46b3b9fa70cdbc69451f9c2d424253c3b69b216d7cc541613\", \"start_char\": 0, \"end_char\": 1809, \"text_sha256\": \"784e57af3594f8d46b3b9fa70cdbc69451f9c2d424253c3b69b216d7cc541613\"}","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"experimental_model","value_text":"Body temperature after paracetamol in cannabinoid receptor 1 and TRPV1 knockout mice with antagonists and fatty acid amide hydrolase manipulation","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"exposure","value_text":"300 milligrams per kilogram paracetamol in knockouts and after AM251 or SB366791, with AM404 given directly","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"limitations","value_text":"Applies the same knockout logic used for analgesia to a different endpoint and gets the opposite answer, which is why both are recorded. Hypothermia below normal is not the same endpoint as antipyresis in fever.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"nutrient_topic","value_text":"Paracetamol research collection; topical membership is not evidence of a direct clinical effect, and the drug is recorded separately from the metabolites NAPQI and AM404.","comparator":null,"unit":null,"notes":"","entity":{"slug":"acetaminophen","display_name":"Paracetamol","entity_type_key":"drug"}},{"dimension":"organism","value_text":"Mouse","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"plain_language","value_text":"The same knockouts that abolish the painkilling leave the temperature drop completely untouched.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"primary_references","value_text":"[apap-p21628499] Paracetamol-induced hypothermia is independent of cannabinoids and transient receptor potential vanilloid-1 and is not mediated by AM404. (2011). https://pubmed.ncbi.nlm.nih.gov/21628499/ DOI: 10.1124/dmd.111.038638","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"tissue_or_cell_type","value_text":"Whole body temperature","comparator":null,"unit":null,"notes":"","entity":null}],"evidence":[{"id":"96725dba-fb34-5496-9c3c-a652471199d3","evidence_kind":"source_excerpt","locator":"Lines 376-387","start_line":376,"end_line":387,"excerpt":"### apap-hypothermia-is-a-different-mechanism\nParacetamol induced hypothermia to the same extent in cannabinoid receptor 1 and TRPV1 knockout mice as in wild-type mice and to the same extent in mice pretreated with the antagonists AM251 or SB366791 as in controls, AM404 failed to induce hypothermia at pharmacological doses, inhibition of fatty acid amide hydrolase did not prevent the development of hypothermia and paracetamol induced hypothermia in fatty acid amide hydrolase knockout mice to the same extent as in wild-type mice, so paracetamol induces hypothermia independent of cannabinoids and TRPV1 and AM404 does not mediate this response.\nCondition category: normal\nnutrient_topic: Paracetamol research collection; topical membership is not evidence of a direct clinical effect, and the drug is recorded separately from the metabolites NAPQI and AM404.\nplain_language: The same knockouts that abolish the painkilling leave the temperature drop completely untouched.\norganism: Mouse\ntissue_or_cell_type: Whole body temperature\nexperimental_model: Body temperature after paracetamol in cannabinoid receptor 1 and TRPV1 knockout mice with antagonists and fatty acid amide hydrolase manipulation\nlimitations: Applies the same knockout logic used for analgesia to a different endpoint and gets the opposite answer, which is why both are recorded. Hypothermia below normal is not the same endpoint as antipyresis in fever.\nexposure: 300 milligrams per kilogram paracetamol in knockouts and after AM251 or SB366791, with AM404 given directly\nevidence_span: {\"source_cache\": \"artifacts/paracetamol-research/21628499.abstract.txt\", \"locator\": \"Indexed abstract; zero-based, end-exclusive Unicode character offsets\", \"file_sha256\": \"784e57af3594f8d46b3b9fa70cdbc69451f9c2d424253c3b69b216d7cc541613\", \"start_char\": 0, \"end_char\": 1809, \"text_sha256\": \"784e57af3594f8d46b3b9fa70cdbc69451f9c2d424253c3b69b216d7cc541613\"}\n[apap-p21628499] Paracetamol-induced hypothermia is independent of cannabinoids and transient receptor potential vanilloid-1 and is not mediated by AM404. (2011). https://pubmed.ncbi.nlm.nih.gov/21628499/ DOI: 10.1124/dmd.111.038638","model_system":"Body temperature after paracetamol in cannabinoid receptor 1 and TRPV1 knockout mice with antagonists and fatty acid amide hydrolase manipulation","directness":"author_interpretation","verification_status":"source_derived_draft","notes":"Exact curation-document quotation, not publisher quotation. Study references: [apap-p21628499] Paracetamol-induced hypothermia is independent of cannabinoids and transient receptor potential vanilloid-1 and is not mediated by AM404. (2011). https://pubmed.ncbi.nlm.nih.gov/21628499/ DOI: 10.1124/dmd.111.038638","relationship":"supports","weight":1.0,"link_notes":"","source":{"id":"9ee11177-f860-5877-bb82-f4ee4acdc538","stable_key":"import-7de430a5-1a36-5231-b931-35cc01d8f3bf","title":"Paracetamol: the enzyme it reduces rather than blocks, the isoform that turned out not to exist, the metabolite that carries the analgesia, and the metabolite that destroys the liver (2026-09-22)","document_type":"imported_text","citation_label":"AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text.","file_path":"","sha256":"9c145887aa10fa7b85f54712e0b41fd9e04fb9544d3182793dd84414dbf8c2ae","revision_id":"c3e7827a-4f10-55e0-97b9-5782b044f7cc","review_status":"unverified_draft","notes":""}}],"relations":[],"conflicts":[{"id":"28ef57c1-0453-5c43-b19f-1d299d9f81f7","title":"Does AM404 carry the effects of paracetamol?","kind":"context_difference","status":"open","why":"For analgesia the case is strong and built from several independent cuts to the same chain: the conjugation does not occur without fatty acid amide hydrolase, the antinociceptive effect of an oral dose is absent in both fatty acid amide hydrolase and TRPV1 knockout mice, central capsazepine abolishes it, cannabinoid receptor 1 antagonists and deletion abolish it while the drug itself does not bind that receptor, and the deacetylated metabolite 4-aminophenol reproduces the entire pharmacological profile of the parent drug. For body temperature the same logic gives the opposite answer: hypothermia is unchanged in cannabinoid receptor 1, TRPV1 and fatty acid amide hydrolase knockout mice, unchanged by either antagonist, and AM404 given directly does not produce it. And in people, although AM404 is now confirmed in cerebrospinal fluid after an intravenous gram, it is present at 5 to 40 nanomoles per litre, which those authors state is far below its documented half-maximal concentration. The reasonable reading is that this drug has at least two mechanisms, that the metabolite route accounts for analgesia in rodents, and that whether it operates at human concentrations is unresolved.","resolution":"Unresolved; needs review.","created_at":"2026-09-22 17:05:56","record_type":"conflict","display_label":"Recorded conflict","record_url":"/conflicts/28ef57c1-0453-5c43-b19f-1d299d9f81f7","sides":[{"conflict_id":"28ef57c1-0453-5c43-b19f-1d299d9f81f7","ordinal":0,"label":"Remove the channel and the painkiller stops working, while putting the metabolite straight into the brain works.","revision_id":"c3e7827a-4f10-55e0-97b9-5782b044f7cc","start_line":311,"end_line":322,"quote":"### apap-analgesia-needs-trpv1\nThe antinociceptive effect of acetaminophen at an oral dose lacking hypolocomotor activity was absent in fatty acid amide hydrolase and TRPV1 knockout mice in the formalin, tail immersion and von Frey tests, that dose did not affect global brain contents of prostaglandin E2 or endocannabinoids, intracerebroventricular injection of AM404 produced a TRPV1-mediated antinociceptive effect in the formalin test, and pharmacological inhibition of brain TRPV1 by intracerebroventricular capsazepine abolished the antinociceptive effect of oral acetaminophen.\nCondition category: machinery_impairment\nnutrient_topic: Paracetamol research collection; topical membership is not evidence of a direct clinical effect, and the drug is recorded separately from the metabolites NAPQI and AM404.\nplain_language: Remove the channel and the painkiller stops working, while putting the metabolite straight into the brain works.\norganism: Mouse\ntissue_or_cell_type: Brain\nexperimental_model: Formalin, tail immersion and von Frey tests in fatty acid amide hydrolase and TRPV1 knockout mice with intracerebroventricular injection\nlimitations: Two separate knockouts and a central antagonist all point the same way, and the dose was chosen to avoid sedation confounding the pain tests. Brain prostaglandin E2 was unchanged at that dose, which is a notable negative.\nexposure: Oral acetaminophen at a dose lacking hypolocomotor activity, with intracerebroventricular AM404 and capsazepine\nevidence_span: {\"source_cache\": \"artifacts/paracetamol-research/20862299.abstract.txt\", \"locator\": \"Indexed abstract; zero-based, end-exclusive Unicode character offsets\", \"file_sha256\": \"2cb3934d80d1a7a6632c49f2007cb6e203b3851706a4ffeb43fda2bb655fa8f2\", \"start_char\": 0, \"end_char\": 1701, \"text_sha256\": \"2cb3934d80d1a7a6632c49f2007cb6e203b3851706a4ffeb43fda2bb655fa8f2\"}\n[apap-p20862299] TRPV1 in brain is involved in acetaminophen-induced antinociception. (2010). https://pubmed.ncbi.nlm.nih.gov/20862299/ DOI: 10.1371/journal.pone.0012748","source_key":"import-7de430a5-1a36-5231-b931-35cc01d8f3bf","source_title":"Paracetamol: the enzyme it reduces rather than blocks, the isoform that turned out not to exist, the metabolite that carries the analgesia, and the metabolite that destroys the liver (2026-09-22)","claim_ids":["bb125c41-c365-5a69-b164-3a375f8840a5"]},{"conflict_id":"28ef57c1-0453-5c43-b19f-1d299d9f81f7","ordinal":1,"label":"The same knockouts that abolish the painkilling leave the temperature drop completely untouched.","revision_id":"c3e7827a-4f10-55e0-97b9-5782b044f7cc","start_line":376,"end_line":387,"quote":"### apap-hypothermia-is-a-different-mechanism\nParacetamol induced hypothermia to the same extent in cannabinoid receptor 1 and TRPV1 knockout mice as in wild-type mice and to the same extent in mice pretreated with the antagonists AM251 or SB366791 as in controls, AM404 failed to induce hypothermia at pharmacological doses, inhibition of fatty acid amide hydrolase did not prevent the development of hypothermia and paracetamol induced hypothermia in fatty acid amide hydrolase knockout mice to the same extent as in wild-type mice, so paracetamol induces hypothermia independent of cannabinoids and TRPV1 and AM404 does not mediate this response.\nCondition category: normal\nnutrient_topic: Paracetamol research collection; topical membership is not evidence of a direct clinical effect, and the drug is recorded separately from the metabolites NAPQI and AM404.\nplain_language: The same knockouts that abolish the painkilling leave the temperature drop completely untouched.\norganism: Mouse\ntissue_or_cell_type: Whole body temperature\nexperimental_model: Body temperature after paracetamol in cannabinoid receptor 1 and TRPV1 knockout mice with antagonists and fatty acid amide hydrolase manipulation\nlimitations: Applies the same knockout logic used for analgesia to a different endpoint and gets the opposite answer, which is why both are recorded. Hypothermia below normal is not the same endpoint as antipyresis in fever.\nexposure: 300 milligrams per kilogram paracetamol in knockouts and after AM251 or SB366791, with AM404 given directly\nevidence_span: {\"source_cache\": \"artifacts/paracetamol-research/21628499.abstract.txt\", \"locator\": \"Indexed abstract; zero-based, end-exclusive Unicode character offsets\", \"file_sha256\": \"784e57af3594f8d46b3b9fa70cdbc69451f9c2d424253c3b69b216d7cc541613\", \"start_char\": 0, \"end_char\": 1809, \"text_sha256\": \"784e57af3594f8d46b3b9fa70cdbc69451f9c2d424253c3b69b216d7cc541613\"}\n[apap-p21628499] Paracetamol-induced hypothermia is independent of cannabinoids and transient receptor potential vanilloid-1 and is not mediated by AM404. (2011). https://pubmed.ncbi.nlm.nih.gov/21628499/ DOI: 10.1124/dmd.111.038638","source_key":"import-7de430a5-1a36-5231-b931-35cc01d8f3bf","source_title":"Paracetamol: the enzyme it reduces rather than blocks, the isoform that turned out not to exist, the metabolite that carries the analgesia, and the metabolite that destroys the liver (2026-09-22)","claim_ids":["3dba7334-c380-548a-a53e-45787fbec7df"]},{"conflict_id":"28ef57c1-0453-5c43-b19f-1d299d9f81f7","ordinal":2,"label":"The metabolite really is in human brain fluid, at about a thousandth of the concentration it is thought to need.","revision_id":"c3e7827a-4f10-55e0-97b9-5782b044f7cc","start_line":363,"end_line":374,"quote":"### apap-am404-in-human-csf-but-low\nCerebrospinal fluid and blood were collected from 26 adult male patients between 10 and 211 minutes after intravenous administration of 1 gram of paracetamol, AM404 was detected in 17 of the 26 evaluable cerebrospinal fluid samples at 5 to 40 nanomoles per litre and paracetamol was measurable within 10 minutes with a maximum measured concentration of 60 micromoles per litre at 206 minutes, the first report of AM404 in human cerebrospinal fluid after paracetamol, although the measured concentrations were far below the previously documented half-maximal inhibitory concentration for this metabolite.\nCondition category: normal\nnutrient_topic: Paracetamol research collection; topical membership is not evidence of a direct clinical effect, and the drug is recorded separately from the metabolites NAPQI and AM404.\nplain_language: The metabolite really is in human brain fluid, at about a thousandth of the concentration it is thought to need.\norganism: Human\ntissue_or_cell_type: Cerebrospinal fluid\nexperimental_model: Cerebrospinal fluid and blood sampled from 26 adult male patients after intravenous paracetamol\nlimitations: The first human demonstration that the metabolite reaches the central nervous system, and simultaneously the strongest quantitative objection to its importance, since the concentrations found are far below the reported potency of the compound.\nexposure: 1 gram intravenous paracetamol, with AM404 measured by liquid chromatography-tandem mass spectrometry\nevidence_span: {\"source_cache\": \"artifacts/paracetamol-research/29238213.abstract.txt\", \"locator\": \"Indexed abstract; zero-based, end-exclusive Unicode character offsets\", \"file_sha256\": \"3f8c752d7c1931585f2ce5bc6059b45b103e73fbc7e067912b0d2c60e8541165\", \"start_char\": 0, \"end_char\": 1557, \"text_sha256\": \"3f8c752d7c1931585f2ce5bc6059b45b103e73fbc7e067912b0d2c60e8541165\"}\n[apap-p29238213] First evidence of the conversion of paracetamol to AM404 in human cerebrospinal fluid. (2017). https://pubmed.ncbi.nlm.nih.gov/29238213/ DOI: 10.2147/jpr.s143500","source_key":"import-7de430a5-1a36-5231-b931-35cc01d8f3bf","source_title":"Paracetamol: the enzyme it reduces rather than blocks, the isoform that turned out not to exist, the metabolite that carries the analgesia, and the metabolite that destroys the liver (2026-09-22)","claim_ids":["87c57968-5510-5a95-8926-59dc05e5a520"]}]}],"corrections":[],"research":null}