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Tytuł:
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Determination of cross tolerance in rat spinal cord using intrathecal infusion via sequential mini-osmotic pumps.
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Autorzy:
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Loomis CW
Milne B
Cervenko FW
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Źródło:
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Pharmacology, biochemistry, and behavior [Pharmacol Biochem Behav] 1987 Jan; Vol. 26 (1), pp. 131-9.
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Typ publikacji:
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Journal Article; Research Support, Non-U.S. Gov't
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Język:
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English
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Imprint Name(s):
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Publication: Tarrytown, NY : Elsevier
Original Publication: Phoenix, N. Y. Ankho International, ltd.
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MeSH Terms:
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Analgesics/*administration & dosage
Morphine/*administration & dosage
Spinal Cord/*drug effects
Animals ; Drug Tolerance ; Injections, Spinal ; Male ; Nociceptors/drug effects ; Norepinephrine/administration & dosage ; Rats ; Rats, Inbred Strains ; Receptors, Opioid/drug effects
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Substance Nomenclature:
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0 (Analgesics)
0 (Receptors, Opioid)
76I7G6D29C (Morphine)
X4W3ENH1CV (Norepinephrine)
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Entry Date(s):
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Date Created: 19870101 Date Completed: 19870511 Latest Revision: 20190712
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Update Code:
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20240104
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DOI:
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10.1016/0091-3057(87)90545-4
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PMID:
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3031695
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Continuous intrathecal (IT) infusion via ALZET mini-osmotic pumps was used to induced spinal tolerance to morphine in the rat. Naloxone (1 mg/kg IP), injected on day 3 of continuous IT morphine (10 micrograms/hr), produced mild withdrawal symptoms in all morphine-treated animals. In rats pretreated with continuous IT morphine (10 micrograms/hr) or saline, systemic morphine (2, 4, 8, 10 and 15 mg/kg IP) produced equivalent, dose-dependent antinociception using the tail-flick and paw pressure tests. The rostral and caudal distribution of methylene blue dye in rat spinal cord was determined on days 1-7 of continuous IT infusion. The dye remained localized near the catheter tip throughout infusion; maximum distribution was 1.5 cm rostrally and 1.0 cm caudally. The data indicate that morphine, infused at the rate of 10 micrograms/hr, does not undergo extensive redistribution in the spinal cord. A sequential, double mini-osmotic pump technique for cross tolerance studies in rat spinal cord is described. In rats pretreated with continuous IT norepinephrine for 4 days, the antinociceptive actions of continuous IT morphine were reduced but not significantly different from saline-pretreated animals. These data suggest that morphine, injected into the spinal cord, does not produce behavioural analgesia by activation of local adrenergic systems.