Supraspinal delta receptor subtype activity of heroin and 6-monoacetylmorphine in Swiss webster mice

Jodie J. Rady, A. E. Takemori, P. S. Portoghese, James M. Fujimoto

Research output: Contribution to journalArticlepeer-review

25 Scopus citations

Abstract

The purpose of this study was to determine which delta (δ) opioid receptor subtype, δ1 or δ2, was involved in producing the antinociceptive action of heroin and 6-monacetylmorphine (MAM) in Swiss Webster mice. Previous work from this laboratory established that heroin and MAM, given intracerebroventricularly (i.c.v.) in Swiss Webster mice, produce antinociception through activation of supraspinal δ receptors. Naltrindole, but not naloxone or nor-binaltorphimine, antagonizes the inhibitory action of heroin and MAM in the tail-flick test. Recent literature documents the occurence of subtypes of the δ opioid receptor and the availability of selective antagonists. 7-Benzylidenenaltrexone (BNTX) antagonizes the antinociception induced by δ1 receptor agonists without affectingthat induced by δ2 receptor agonists. Naltriben (NTB) selectively inhibits δ2- but not δ1-induced antinociception. In the present study BNTX and NTB were administered i.c.v. with heroin and MAM to determine the δ receptor subtype responsible for inhibition of the tail-flick response in Swiss Webster mice. The ED50 for heroin-induced antinociception was increased 19-fold by BNTX and was not altered by NTB administration. On the other hand, the ED50 value of MAM was increased 3-fold by NTB and was not altered b by BNTX administration. These results suggest that heroin activated supraspinal δ1 receptors and MAM acted on supraspinal δ2 receptors to produce antinociception in Swiss Webster mice.

Original languageEnglish (US)
Pages (from-to)603-609
Number of pages7
JournalLife Sciences
Volume55
Issue number8
DOIs
StatePublished - 1994

Keywords

  • 6-monoacetylmorphine
  • delta subtype
  • heroin
  • δ opioid receptors

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