Modification of different morphine actions by 6-hydroxydopamine and 6-hydroxydopamine plus desmethylimipramine.
After intracisternal 6-hydroxydopamine (6-OHDA) in mice, brain noradrenaline (NA) and dopamine (DA) are diminished, although the reduction of NA is more pronounced. Intracisternal injection of 6-OHDA in desmethylimipramine (DMI)-pretreated animals strengthens the depletion of DA while NA is partly protected. The concentration of 5-hydroxytryptamine (5-HT) is not influenced by 6-OHDA or 6-OHDA + DMI. Chronic morphine treatment to some extent enhances reduced NA and DA levels after 6-OHDA, but the decreased central catecholamine (CA) content after 6-OHDA + DMI is not raised. Morphine analgesia is highly attenuated in 6-OHDA and 6-OHDA + DMI mice. The reduction occurs in non-tolerant as well as in tolerant animals. The acute effect of morphine on body temperature is abolished with 6-OHDA, but not with 6-OHDA + DMI, whereas the interaction of central CA in morphine-induced running shows distinctly marked reduction with 6-OHDA + DMI, but not with 6-OHDA. Acute toxicity is enhanced by 6-OHDA + DMI whereas the development of tolerance against the toxicity of morphine is diminished by 6-OHDA. Lack of CA in the brain decreases sensitivity against naloxone withdrawal in acute as well as in chronic experiments.
D000698:Analgesia; D000818:Animals; D001831:Body Temperature / Q000187:drug effects; D001923:Brain Chemistry / Q000187:drug effects; D003891:Desipramine / Q000494:pharmacology*; D004347:Drug Interactions; D006801:Humans; D006892:Hydroxydopamines / Q000494:pharmacology*; D008297:Male; D051379:Mice; D009020:Morphine / Q000494:pharmacology* / Q000633:toxicity; D009021:Morphine Dependence / Q000503:physiopathology; D009043:Motor Activity / Q000187:drug effects
D006892:Hydroxydopamines; D009020:Morphine; D003891:Desipramine