The Effects of Dopamine Receptor Agents on Swim Stress-Induced Inhibition of Naloxone-Induced Jumping Behavior in Morphine-Dependent Mice

In the present study, interactions of dopamine receptor agonists and antagonists with waterswimming stress (wss) on naloxone-induced jumping in morphine-dependent mice wereexamined. mice were rendered dependent as described in the methods section. the opioidreceptor antagonist, naloxone (l mg/kg), was injected to elicit jumping (as a withdrawalsign). the first group exposed to wss in the presence or absence of dopamine receptor drugs,before naloxone injection, in order to test the interaction of dopamine receptor mechanismswith wss on expression of jumping behavior. when the animals were exposed to wss forperiods of 0.5, i or 3 min, is min prior to naloxone injection, wss administration for a periodof 3 min decreased the expression of jumping, but not diarrhea induced by naloxone. the direceptor agonist, skf38393 (1-phenyl-7,8-dihydroxy-2,3,4,5-tetrahydro-lh-3-benzazepinehydrochloride; 8 and 16 mg/kg), dl receptor antagonist, sch 23390 (r-(+)-8-chloro-2,3,4,5tetrahydro-3-methyl-5-phenyl-lhbenzazepine=7-01 maleate; 0.0025 and 0.005 mglkg) , d2receptor agonist, quinpirole (0.3 and 0.5 mg/kg) and d2 receptor antagonist, sulpiride (50mglkg), potentiated the inhibition of jumping induced by wss. quinpirole, but not otherdopamine receptor agent s, increased diarrhea. in the second group of animals, effects of thedopamine receptor drugs; during development of morph ine dependence, in the presence ofwss administration were tested . admini strat ion of apomorphine (1 and 2 mg/kg ) or skf38393 (8 mg/kg ) in the presence of wss, during the developm ent of morphine dependenceincreased jumping, while quinpirole (0.5 mg/kg) decrea sed diarrhea . in contrary, neithersulpiride nor sch 23390 did not alter jumping or diarrhea induced by naloxone. it could beconcluded that dopamine receptor mechanism(s) and/or wss could be related the developmentof morph ine dependency.