Abstract
We evaluated the effect of selective opioid peptides and naltrexone on feeding when injected into the nucleus of the solitary tract (NTS). Doses of 0, 1, 2, 4, and 8 nmol of [D-Ala2,N-Me-Phe4,Gly5-ol]enkephalin (DAMGO, mu-agonist), dynorphin A-(1-17) (DynA-(1-17), kappa-agonist), and [D-Ser2]leucine enkephalin-thr, (delta-agonist) were injected into the NTS in satiated male rats, and food intake was measured at 1, 2, and 4 h. Only DAMGO significantly increased feeding above control levels at doses of 2, 4, and 8 nmol. Doses of 10 and 50 microg naltrexone in the NTS significantly decreased 18-h deprivation-induced feeding. These data suggest that NTS opioid receptors (primarily mu) may be involved in the regulation of feeding.
MeSH terms
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Analgesics / administration & dosage
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Analgesics / pharmacology
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Animals
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Dose-Response Relationship, Drug
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Dynorphins / administration & dosage
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Dynorphins / pharmacology*
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Enkephalin, Ala(2)-MePhe(4)-Gly(5)-
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Enkephalin, Leucine / administration & dosage
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Enkephalin, Leucine / analogs & derivatives*
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Enkephalin, Leucine / pharmacology
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Enkephalins / administration & dosage
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Enkephalins / pharmacology*
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Feeding Behavior / drug effects*
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Male
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Microinjections
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Naltrexone / administration & dosage
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Naltrexone / pharmacology
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Rats
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Rats, Sprague-Dawley
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Solitary Nucleus / drug effects
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Solitary Nucleus / physiology*
Substances
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Analgesics
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Enkephalins
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Enkephalin, Ala(2)-MePhe(4)-Gly(5)-
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Enkephalin, Leucine
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Naltrexone
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Dynorphins
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enkephalin, Ser(2), Leu(5), Thr(6)-