Motivational effects mu- and kappa-opioid agonists following acute and chronic restraint stress: involvement of dopamine D(1) and D(2) receptors.
The influence of both acute and chronic restraint stress on the rewarding properties of morphine (1, 2 or 3 mg/kg i.p.) and the aversive effects of naloxone (0.5 mg/kg i.p. x3 or 1.0 mg/kg i.p.) or bremazocine (0.4 mg/kg i.p.) was investigated. An acute (2 h) but not chronic restraint (2 h daily for 7 days) enhanced the morphine place preference, and elicited a place aversion with a subthreshold dose of bremazocine. This enhancing effect on the reinforcing properties induced by the drugs was prevented by either R(+)-SCH-23390 hydrochloride (R(+)-7-chloro-8-hydroxy-3-methyl-1-phenyl-2,3,4,5-tetrahydro-1H3-benzazepine, 30 microg/kg i.p.) or (+/-)-sulpiride (60 mg/kg i.p.), 10-20 min prior to the stress session. Naltrexone pretreatment (1 mg/kg i.p.) abolished the stress effect on morphine place preference but not that on bremazocine aversion. Instead, nor-BNI (30 microg/3 microl i.c.v.) abolished the stress's effects on bremazocine aversion, but did not modify those on morphine preference. These results show that: (1) acute stress enhanced the morphine and bremazocine conditioned reinforcing effects meanwhile chronic stress did not modify them; (2) the stimulation of D(1) and D(2) dopamine receptors is necessary for the development of restraint stress-induced sensitization to the conditioned reinforcing effects of drugs; and (3) the stimulation mu/delta- and kappa-opioid receptors seems to be differentially involved.
del Rosario Capriles
Nancy
N
Departamento de Farmacología, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, 5000 Córdoba, Argentina.
Cancela
Liliana Marina
LM
D000208:Acute Disease; D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects*; D001575:Benzomorphans / Q000494:pharmacology; D002908:Chronic Disease; D003216:Conditioning, Operant / Q000187:drug effects; D007276:Injections, Intraventricular; D008297:Male; D009020:Morphine / Q000494:pharmacology; D009270:Naloxone / Q000494:pharmacology; D009271:Naltrexone / Q000031:analogs & derivatives* / Q000494:pharmacology; D009292:Narcotic Antagonists / Q000494:pharmacology; D009294:Narcotics / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D017447:Receptors, Dopamine D1 / Q000187:drug effects*; D017448:Receptors, Dopamine D2 / Q000187:drug effects*; D017473:Receptors, Opioid, kappa / Q000819:agonists*; D017450:Receptors, Opioid, mu / Q000819:agonists*; D013315:Stress, Psychological / Q000523:psychology*
D001575:Benzomorphans; D009292:Narcotic Antagonists; D009294:Narcotics; D017447:Receptors, Dopamine D1; D017448:Receptors, Dopamine D2; D017473:Receptors, Opioid, kappa; D017450:Receptors, Opioid, mu; D009270:Naloxone; C051844:norbinaltorphimine; D009271:Naltrexone; D009020:Morphine; C027248:bremazocine