Similarities and differences between d-ALA2 MET5 enkephalin amide and morphine in the induction of tolerance to their effects on catalepsy and on dopamine metabolism in the rat brain

M. G. De Simoni, V. Guardabasso, K. Misterek, S. ALgeri

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11 Citations (Scopus)

Abstract

Rats were made tolerant to morphine or to DALA, a synthetic analogue of met-enkephalin, by prolonged exposure to these compounds. Tolerance was assessed by evaluating the resistance of the treated rats to present catalepsy after an acute dose of the opiates. Both morphine and DALA induced tolerance and cross-tolerance to the cataleptic effect. Acute administration of morphine and DALA increased the concentration of DOPAC in striatum, limbic area and s.nigra of control rats. This increase was not present when morphine was given acutely to chronically morphine-treated rats, indicating that these animals were tolerant to this effect. Chronically morphine-treated rats given DALA presented partial tolerance to the biochemical effect of the peptide in limbic area and in s.nigra but not in striatum, indicating that only in certain areas was crosstolerance produced by chronic morphine. When DALA was administered at different doses to chronically DALA treated rats, the peptide induced rise in DA catabolite was similar to that produced in control animals, so clearly there was no tolerance to this biochemical effect. In these animals cross tolerance to morphine's effect on DA metabolism was present in s.nigra but not in the other two areas, indicating that s.nigra is particularly sensitive to opiate-induced tolerance on DA metabolism.

Original languageEnglish
Pages (from-to)105-111
Number of pages7
JournalNaunyn-Schmiedeberg's Archives of Pharmacology
Volume321
Issue number2
DOIs
Publication statusPublished - Nov 1982

Fingerprint

Catalepsy
Enkephalins
Amides
Morphine
Dopamine
Brain
Opiate Alkaloids
3,4-Dihydroxyphenylacetic Acid
Methionine Enkephalin
Peptides
Ala(2)-enkephalinamide-met

Keywords

  • Catalepsy
  • d-Ala Met enkephalin amide
  • DOPAC levels
  • Morphine
  • Tolerance

ASJC Scopus subject areas

  • Pharmacology

Cite this

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title = "Similarities and differences between d-ALA2 MET5 enkephalin amide and morphine in the induction of tolerance to their effects on catalepsy and on dopamine metabolism in the rat brain",
abstract = "Rats were made tolerant to morphine or to DALA, a synthetic analogue of met-enkephalin, by prolonged exposure to these compounds. Tolerance was assessed by evaluating the resistance of the treated rats to present catalepsy after an acute dose of the opiates. Both morphine and DALA induced tolerance and cross-tolerance to the cataleptic effect. Acute administration of morphine and DALA increased the concentration of DOPAC in striatum, limbic area and s.nigra of control rats. This increase was not present when morphine was given acutely to chronically morphine-treated rats, indicating that these animals were tolerant to this effect. Chronically morphine-treated rats given DALA presented partial tolerance to the biochemical effect of the peptide in limbic area and in s.nigra but not in striatum, indicating that only in certain areas was crosstolerance produced by chronic morphine. When DALA was administered at different doses to chronically DALA treated rats, the peptide induced rise in DA catabolite was similar to that produced in control animals, so clearly there was no tolerance to this biochemical effect. In these animals cross tolerance to morphine's effect on DA metabolism was present in s.nigra but not in the other two areas, indicating that s.nigra is particularly sensitive to opiate-induced tolerance on DA metabolism.",
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T1 - Similarities and differences between d-ALA2 MET5 enkephalin amide and morphine in the induction of tolerance to their effects on catalepsy and on dopamine metabolism in the rat brain

AU - De Simoni, M. G.

AU - Guardabasso, V.

AU - Misterek, K.

AU - ALgeri, S.

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AB - Rats were made tolerant to morphine or to DALA, a synthetic analogue of met-enkephalin, by prolonged exposure to these compounds. Tolerance was assessed by evaluating the resistance of the treated rats to present catalepsy after an acute dose of the opiates. Both morphine and DALA induced tolerance and cross-tolerance to the cataleptic effect. Acute administration of morphine and DALA increased the concentration of DOPAC in striatum, limbic area and s.nigra of control rats. This increase was not present when morphine was given acutely to chronically morphine-treated rats, indicating that these animals were tolerant to this effect. Chronically morphine-treated rats given DALA presented partial tolerance to the biochemical effect of the peptide in limbic area and in s.nigra but not in striatum, indicating that only in certain areas was crosstolerance produced by chronic morphine. When DALA was administered at different doses to chronically DALA treated rats, the peptide induced rise in DA catabolite was similar to that produced in control animals, so clearly there was no tolerance to this biochemical effect. In these animals cross tolerance to morphine's effect on DA metabolism was present in s.nigra but not in the other two areas, indicating that s.nigra is particularly sensitive to opiate-induced tolerance on DA metabolism.

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