Differential Conditioned Place Preference Responses to Endomorphin-1 and Endomorphin-2 Microinjected into the Posterior Nucleus Accumbens Shell and Ventral Tegmental Area in the Rat
An unbiased conditioned place preference (CPP) paradigm was used to evaluate the reward effects of endogenous μ-opioid receptor ligands endomorphin-1 (EM-1) and endomorphin-2 (EM-2) from the mesolimbic posterior nucleus accumbens (Acb) shell and the ventral tegmental area (VTA) in CD rats. EM-1 (1....
Saved in:
Published in | The Journal of pharmacology and experimental therapeutics Vol. 309; no. 2; pp. 816 - 824 |
---|---|
Main Authors | , , , , , , |
Format | Journal Article |
Language | English |
Published |
United States
American Society for Pharmacology and Experimental Therapeutics
01.05.2004
|
Subjects | |
Online Access | Get full text |
Cover
Loading…
Summary: | An unbiased conditioned place preference (CPP) paradigm was used to evaluate the reward effects of endogenous μ-opioid receptor
ligands endomorphin-1 (EM-1) and endomorphin-2 (EM-2) from the mesolimbic posterior nucleus accumbens (Acb) shell and the
ventral tegmental area (VTA) in CD rats. EM-1 (1.6-8.1 nmol) microinjected into posterior Acb shell produced CPP, whereas
EM-2 (8.7-17.5 nmol) given into the same Acb shell produced conditioned place aversion (CPA). EM-1 (1.6-16.3 nmol) microinjected
into the VTA produced CPP, whereas EM-2 (8.7 and 17.5 nmol) given into the same VTA site did not produce any effect, but at
a high dose (35 nmol) produced CPP. EM-1 (3.3 nmol) or EM-2 (17.5 nmol) microinjected into the nigrostriatal substantia nigra
was not significantly different from vehicle-injected groups. d -Phe-Cys-Tyr- d -Trp-Orn-Thr-Pen-Thr-NH 2 (CTOP) at 94.13 pmol or 3-methoxynaltrexone at 0.64 pmol microinjected into the posterior Acb shell blocked EM-1-induced
CPP and EM-2-induced CPA. At a higher dose, CTOP (941.3 pmol) and 3-methoxynaltrexone (6.4 pmol) produced CPA and CPP, respectively.
Coadministration with antiserum against dynorphin A(1-17) (Dyn) (10 μg) microinjected into the posterior Acb shell blocked
EM-2-induced CPA. However, it did not affect EM-1-induced CPP. It is concluded that EM-1 and EM-2 produce site-dependent CPP
and CPA, respectively, by stimulation of different subtypes of μ-opioid-receptors; stimulation of one subtype of μ-opioid-receptor
at the posterior Acb shell and VTA by EM-1 induces CPP, whereas stimulation of another subtype of μ-opioid receptor at the
posterior Acb shell, but not the VTA, by EM-2 induces the release of Dyn to produce CPA. |
---|---|
Bibliography: | ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 |
ISSN: | 0022-3565 1521-0103 |
DOI: | 10.1124/jpet.103.059287 |