The World Health Organization has reported that when morp @entity1286 used to control pain @entity158 canc @entity5 i @entity1 yc @entity734 not a major concern. Our studies were undertaken to ascertain the modulation of psyc @entity734 morp @entity1286 er a chronic pain @entity158 e state in rats @entity35 rp @entity1286 uced a dose-dependent place preference. We found that inflammatory and neur @entity9 e states significantly suppressed the morp @entity1286 uced rewarding effect. In an inflammatory pain @entity158 e state, the suppressive effect was significantly recovered by treatment with a k-opioid receptor antagonist. In addition, in vivo microdialysis studies clearly showed that the morp @entity1286 uced increase in the extracellular levels of dopa @entity935 ) in the nucleus accumbens (N.Acc.) was significantly decreased in rats @entity35 treated with form @entity406 is effect was in turn reversed by the microinjection of a specific dynorphin A antibody into the N.Acc. These findings suggest that the inflammatory pain @entity158 e state may have caused the sustained activation of the k-opioidergic system within the N.Acc., resulting in suppression of the morp @entity1286 uced rewarding effect in rats @entity35 the other hand, we found that attenuation of the morp @entity1286 uced place preference under neur @entity9 result from a decrease in the morp @entity1286 uced DA release in the N.Acc with a reduction in the  -opioid receptor-mediated G-protein activation in the ventral tegmental area (VTA). Moreover, nerv @entity128 ults in the continuous release of endogenous b-endorphin to cause the dysfunction of  -opioid receptors in the VTA. This paper also provides a review to clarify misunderstandings of opioid analgesic use to control pain @entity158 canc @entity5 i @entity1

Treatment of XXXX and Medical Narcotics.

@entity1 :: ('9606', 'Species') :: ['patients'] @entity5 :: ('MESH:D009369', 'Disease') :: ['cancer'] @entity935 :: ('MESH:D004298', 'Chemical') :: ['dopamine'] @entity406 :: ('MESH:D005557', 'Chemical') :: ['formalin'] @entity128 :: ('MESH:D020209', 'Disease') :: ['nerve injury'] @entity158 :: ('MESH:D010146', 'Disease') :: ['pain'] @entity1286 :: ('MESH:D009020', 'Chemical') :: ['morphine', 'Morphine'] @entity35 :: ('10116', 'Species') :: ['rats'] @entity734 :: ('MESH:D019966', 'Disease') :: ['psychological dependence'] @entity9 :: ('MESH:D009437', 'Disease') :: ['neuropathic pain']
@entity5 :: (MESH:D009369,Disease) :: ['Cancer Pain']
