Abstract
Itch is thought to be signaled by pruritogen-responsive neurons in the superficial spinal dorsal horn. Many neurons here express the substance P NK-1 receptor. We investigated whether neurotoxic destruction of spinal NK-1-expressing neurons affected itch-related scratching behavior. Rats received intracisternal substance P conjugated to saporin (SP-SAP), or saporin (SAP) only (controls), and were subsequently tested for scratching behavior elicited by intradermal 5-hydroxytryptamine. SAP controls exhibited dose-related hindlimb scratching, which was significantly attenuated in SP-SAP-treated rats. There was a virtual absence of NK-1 immunoreactive neurons in superficial laminae of the upper cervical and medullary dorsal horn in SP-SAP-treated rats. These results indicate that superficial dorsal horn neurons expressing NK-1 receptors play a key role in spinal itch transmission.
Publication types
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Research Support, N.I.H., Extramural
MeSH terms
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Animals
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Drug Combinations
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Hindlimb / drug effects
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Hindlimb / physiopathology
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Immunohistochemistry
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Injections, Intradermal
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Male
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Microinjections
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Neurotransmitter Agents / administration & dosage
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Neurotransmitter Agents / pharmacology*
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Posterior Horn Cells / drug effects
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Posterior Horn Cells / metabolism*
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Pruritus / chemically induced
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Pruritus / drug therapy*
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Pruritus / physiopathology
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Rats
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Rats, Sprague-Dawley
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Receptors, Neurokinin-1 / drug effects
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Receptors, Neurokinin-1 / metabolism*
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Ribosome Inactivating Proteins, Type 1 / administration & dosage
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Ribosome Inactivating Proteins, Type 1 / pharmacology*
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Saporins
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Serotonin
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Serotonin Agents
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Substance P / administration & dosage
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Substance P / pharmacology*
Substances
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Drug Combinations
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Neurotransmitter Agents
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Receptors, Neurokinin-1
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Ribosome Inactivating Proteins, Type 1
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Serotonin Agents
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Serotonin
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Substance P
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Saporins