Abstract
We examined and compared the effects of intrathecal (i.t.) endomorphin-1 and endomorphin-2 on the nociceptive flexor reflex in decerebrate, spinalized, unanesthetized rats. I.t. endomorphin-1 and -2 induced a dose-dependent depression of the flexor reflex with an initial brief facilitatory effect. The magnitude of reflex facilitation and depression was similar between endomorphin-1 and -2, but the duration of depression was significantly longer for endomorphin-1 than endomorphin-2. The results suggested that the spinal antinociceptive effects of endomorphin-1 and -2 are similar, with endomorphin-1 being more resistant to enzymatic degradation.
Publication types
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Comparative Study
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Research Support, Non-U.S. Gov't
MeSH terms
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Afferent Pathways / drug effects
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Afferent Pathways / metabolism
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Analgesics, Opioid / metabolism*
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Analgesics, Opioid / pharmacology
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Animals
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Carboxypeptidases / metabolism
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Dose-Response Relationship, Drug
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Female
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Injections, Spinal
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Muscle Contraction / drug effects
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Muscle Contraction / physiology
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Nerve Fibers / drug effects
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Nerve Fibers / metabolism
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Neurons / drug effects
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Neurons / metabolism
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Nociceptors / drug effects
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Nociceptors / metabolism*
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Oligopeptides / metabolism*
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Oligopeptides / pharmacology
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Pain / drug therapy
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Pain / metabolism*
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Pain / physiopathology
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Rats
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Rats, Sprague-Dawley
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Receptors, Opioid, mu / drug effects
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Receptors, Opioid, mu / metabolism
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Reflex / drug effects
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Reflex / physiology*
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Spinal Cord / drug effects
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Spinal Cord / metabolism*
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Synaptic Transmission / drug effects
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Synaptic Transmission / physiology
Substances
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Analgesics, Opioid
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Oligopeptides
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Receptors, Opioid, mu
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endomorphin 1
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endomorphin 2
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Carboxypeptidases