Abstract
We investigated and compared the effects of two amphibian tachykinins, the NK1 receptor agonist PG-SPI and the NK3 receptor agonist PG-KII, and the mammalian tachykinins substance P, neurokinin A and neurokinin B on the reaction time to a painful radiant heat stimulus (tail-flick test in rats) after intracerebroventricular injection. PG-SPI (1, 10 and 20 microg) and PG-KII (1, 5 and 10 microg) significantly increased the reaction time. Substance P (10 microg) injected intracerebroventricularly induced antinociception, whereas neurokinin A and neurokinin B did not. Like analgesia evoked by exogenous substance P, PG-SPI-evoked analgesia was blocked by pretreatment with naloxone. Naloxone left PG-KII antinociception unchanged, but the NK3 receptor selective antagonist markedly reduced it. These findings suggest NK1 and NK3 tachykinin receptor system involvement in supraspinal analgesia in rats.
MeSH terms
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Analgesia
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Animals
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Dose-Response Relationship, Drug
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Hot Temperature
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Indoles / pharmacology
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Male
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Naloxone / pharmacology
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Narcotic Antagonists / pharmacology
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Neurokinin A / pharmacology
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Neurokinin B / pharmacology
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Neurokinin-1 Receptor Antagonists
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Oligopeptides / administration & dosage
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Oligopeptides / pharmacology*
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Pain Measurement
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Pain Threshold
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Piperidines / pharmacology
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Pyrrolidonecarboxylic Acid / analogs & derivatives
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Quinuclidines / pharmacology
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Rats
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Rats, Wistar
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Receptors, Neurokinin-1 / agonists
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Receptors, Neurokinin-3 / agonists
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Receptors, Neurokinin-3 / antagonists & inhibitors
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Substance P / pharmacology
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Tachykinins / administration & dosage
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Tachykinins / pharmacology*
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Time Factors
Substances
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Indoles
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Narcotic Antagonists
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Neurokinin-1 Receptor Antagonists
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Oligopeptides
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PG-KII peptide
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Piperidines
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Quinuclidines
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R 486
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R 820
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Receptors, Neurokinin-1
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Receptors, Neurokinin-3
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Tachykinins
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pyroglutamyl-prolyl-asparaginyl-prolyl-aspartyl-glutamyl-phenylalanyl-phenylalanyl-glycyl-leucyl-methioninamide
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SR 140333
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Substance P
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Naloxone
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Neurokinin A
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Neurokinin B
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Pyrrolidonecarboxylic Acid