The effect of morphine tolerance dependence and abstinence on immunoreactive dynorphin (1-13) levels in discrete brain regions, spinal cord, pituitary gland and peripheral tissues of the rat.
The effect of morphine tolerance dependence and protracted abstinence on the levels of dynorphin (1-13) in discrete brain regions, spinal cord, pituitary gland and peripheral tissues was determined in male Sprague-Dawley rats. Of all the tissues examined, the highest level of dynorphin (1-13) was found to be in the pituitary gland. Among the brain regions and spinal cord examined, the levels of dynorphin (1-13) in descending order were: hypothalamus, spinal cord, midbrain, pons and medulla, hippocampus, cortex, amygdala and striatum. The descending order for the levels of dynorphin (1-13) in peripheral tissues was: adrenals, heart and kidneys. In morphine tolerant rats, the levels of dynorphin (1-13) increased in amygdala but were decreased in pons and medulla. In morphine abstinent rats, the levels of dynorphin (1-13) were increased in amygdala, hypothalamus and hippocampus. The levels of dynorphin (1-13) were increased in pituitary but decreased in spinal cord and remained so even during protracted abstinence. The levels of dynorphin (1-13) in the peripheral tissues of morphine tolerant rats were unaffected. However, in the heart and kidneys of morphine abstinent rats, the levels of dynorphin (1-13) were increased significantly. It is concluded that both morphine tolerance and abstinence modify the levels of dynorphin (1-13) in pituitary, central and peripheral tissues. Morphine abstinence differed from non-abstinence process in that there were additional changes (increases) in the levels of dynorphin (1-13) in brain regions (hypothalamus and hippocampus) and peripheral tissues (heart and kidneys) and may contribute to the symptoms of the morphine abstinence syndrome.(ABSTRACT TRUNCATED AT 250 WORDS)
Rattan
A K
AK
Department of Pharmacology, College of Medicine, Ohio State University, Columbus 43210.
Koo
K L
KL
Tejwani
G A
GA
Bhargava
H N
HN
D000311:Adrenal Glands / Q000187:drug effects / Q000378:metabolism; D000700:Analgesics / Q000378:metabolism*; D000818:Animals; D001923:Brain Chemistry / Q000187:drug effects; D004361:Drug Tolerance; D004399:Dynorphins / Q000276:immunology / Q000378:metabolism*; D006321:Heart / Q000187:drug effects; D007668:Kidney / Q000187:drug effects / Q000378:metabolism; D008297:Male; D009020:Morphine / Q000494:pharmacology*; D009021:Morphine Dependence / Q000378:metabolism*; D009206:Myocardium / Q000378:metabolism; D010446:Peptide Fragments / Q000276:immunology / Q000378:metabolism*; D010902:Pituitary Gland / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D013116:Spinal Cord / Q000187:drug effects / Q000378:metabolism; D013375:Substance Withdrawal Syndrome / Q000378:metabolism*
D000700:Analgesics; D010446:Peptide Fragments; C026843:dynorphin (1-13); D004399:Dynorphins; D009020:Morphine