title: Amitriptyline induces nuclear transcription factor-kappaB-dependent glutamate transporter upregulation in chronic morphine-infused rats.
abstract: We previously showed that intrathecal co-administration of amitriptyline with morphine upregulates the expression of the glial glutamate transporters glutamate-aspartate transporter (GLAST) and glutamate transporter-1 (GLT-1) and restores neuronal glutamate transporter excitatory amino acid carrier 1 (EAAC1) expression in chronically morphine-infused rats. The present study examined the role of nuclear transcription factor-kappaB (NF-kappaB) in the regulation of the expression of GLAST, GLT-1, and EAAC1 following long-term amitriptyline/morphine co-infusion. Male Wistar rats were implanted with two intrathecal catheters with or without a microdialysis probe; one of the catheters was used for continuous infusion of saline (control), morphine (15 microg/h), or morphine plus amitriptyline (both 15 microg/h) for 5 days, while the other was used for a single daily intrathecal injection of the NF-kappaB inhibitor Ro106-9920 (10 microl of 10 microM) for 5 days. We found that amitriptyline co-infusion restored the antinociceptive effect of morphine (4.5-fold right-shift in the morphine dose-response curve compared with a 65-fold right-shift in its absence) and this effect was inhibited by Ro106-9920 administration (48-fold right-shift). Moreover, amitriptyline/morphine co-infusion increased IkappaBalpha phosphorylation and the translocation of NF-kappaB p65 from the cytosol to the nucleus. Daily intrathecal injection of Ro106-9920 prevented the amitriptyline/morphine-induced NF-kappaB p65 translocation and reversed the amitriptyline/morphine-induced GLAST and GLT-1 upregulation and inhibited the restoration of EAAC1 expression. The Ro106-9920 injections abolished the inhibitory effect of amitriptyline on the morphine-evoked release of excitatory amino acids into the spinal cerebrospinal fluid (CSF) dialysates. In conclusion, amitriptyline/morphine co-infusion restores the antinociceptive effect of morphine and upregulates GLAST and GLT-1 expression and restores EAAC1 expression to baseline levels, thus reducing excitatory amino acid levels in the spinal CSF dialysates. The mechanism involves activation of the NF-kappaB pathway, but may also involve other pathways.
authors.affiliation: Department of Anesthesiology, Tri-service General Hospital and National Defense Medical Center, Taipei, Taiwan.
authors.forename: Y-H
authors.initials: YH
authors.lastname: Tai
authors.forename: R-Y
authors.initials: RY
authors.lastname: Tsai
authors.forename: Y-H
authors.initials: YH
authors.lastname: Wang
authors.forename: C-H
authors.initials: CH
authors.lastname: Cherng
authors.forename: P-L
authors.initials: PL
authors.lastname: Tao
authors.forename: T-M
authors.initials: TM
authors.lastname: Liu
authors.forename: C-S
authors.initials: CS
authors.lastname: Wong
mesh_terms: D018759:Adrenergic Uptake Inhibitors / Q000008:administration & dosage*; D027322:Amino Acid Transport System X-AG / Q000187:drug effects* / Q000378:metabolism; D000639:Amitriptyline / Q000008:administration & dosage*; D000818:Animals; D015153:Blotting, Western; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D004361:Drug Tolerance / Q000502:physiology; D018846:Excitatory Amino Acids / Q000378:metabolism; D005455:Fluorescent Antibody Technique; D005786:Gene Expression Regulation / Q000187:drug effects; D007091:Image Processing, Computer-Assisted; D007278:Injections, Spinal; D008297:Male; D017551:Microdialysis; D009020:Morphine / Q000494:pharmacology; D016328:NF-kappa B / Q000187:drug effects* / Q000378:metabolism; D009294:Narcotics / Q000494:pharmacology*; D017288:Pain Threshold / Q000187:drug effects; D051381:Rats; D017208:Rats, Wistar; D013454:Sulfoxides / Q000494:pharmacology; D013777:Tetrazoles / Q000494:pharmacology; D015854:Up-Regulation
chemical_list: D018759:Adrenergic Uptake Inhibitors; D027322:Amino Acid Transport System X-AG; D018846:Excitatory Amino Acids; D016328:NF-kappa B; D009294:Narcotics; C461648:Ro 106-9920; D013454:Sulfoxides; D013777:Tetrazoles; D000639:Amitriptyline; D009020:Morphine