The Effects of Dopamine Receptor Agents on Swim Stress-Induced Inhibition of Naloxone-Induced Jumping Behavior in Morphine-Dependent Mice
Iranian Journal of Pharmaceutical Research
In the present study, interactions of dopamine receptor agonists and antagonists with water swimming stress (WSS) on naloxone-induced jumping in morphine-dependent mice were examined. Mice were rendered dependent as described in the methods section. The opioid receptor antagonist, naloxone (1 mg/kg), was injected to elicit jumping (as a withdrawal sign). The first group exposed to WSS in the presence or absence of dopamine receptor drugs, before naloxone injection, in order to test the
... o test the interaction of dopamine receptor mechanisms with WSS on expression of jumping behavior. When the animals were exposed to WSS for periods of 0.5, 1 or 3 min, 15 min prior to naloxone injection, WSS administration for a period of 3 min decreased the expression of jumping, but not diarrhea induced by naloxone. The D1 receptor agonist, SKF38393 (1-phenyl-7,8-dihydroxy-2,3,4,5-tetrahydro-1H-3-benzazepine hydrochloride; 8 and 16 mg/kg), D1 receptor antagonist, SCH 23390 (R-(+)-8-chloro-2,3,4,5tetrahydro-3-methyl-5-phenyl-1Hbenzazepine=7-ol maleate; 0.0025 and 0.005 mg/kg), D2 receptor agonist, quinpirole (0.3 and 0.5 mg/kg) and D2 receptor antagonist, sulpiride (50 mg/kg), potentiated the inhibition of jumping induced by WSS. Quinpirole, but not other dopamine receptor agents, increased diarrhea. In the second group of animals, effects of the dopamine receptor drugs; during development of morphine dependence, in the presence of WSS administration were tested. Administration of apomorphine (1 and 2 mg/kg) or SKF 38393 (8 mg/kg) in the presence of WSS, during the development of morphine dependence increased jumping, while quinpirole (0.5 mg/kg) decreased diarrhea. In contrary, neither sulpiride nor SCH 23390 did not alter jumping or diarrhea induced by naloxone. It could be concluded that dopamine receptor mechanism(s) and/or WSS could be related the development of morphine dependency.