Neurotransmitter uptake in various brain regions of chronically morphinized rats.
Rats were long-term morphine-intoxicated by a fluid-diet model ensuring an equal nutrient intake in morphinized and control rats. Uptake of neurotransmitters and D-ala2-met5-enkephalinamide (Enk) was studied in the particulate fractions (obtained at 10,000 g) from well defined brain regions of long-term intoxicated and morphine withdrawn rats. In control animals the accumulation of [3H]glutamate and [3H]gamma-aminobutyric acid (GABA) reached the highest tissue/medium (T/M) ratio values, 30-120, in the regions studied while monoamine T/M values were 2-10. No active uptake of [3H]Enk could be demonstrated. Striatum showed the most evident modifications in neurotransmitter uptake. In this region the equilibrium T/M ratio for [3H]glutamate and [3H]GABA was significantly lower in intoxicated rats versus controls. Moreover, the T/M ratio for [3H]5-hydroxytryptamine (5-HT) was lower, while that for [3H]dopamine (DA) was higher in abstinent rats in comparison with the controls. [3H]glutamate and [3H]GABA uptakes were also significantly lower, respectively, in frontal cortex, hippocampus and brain stem in intoxicated rats, while [3H]5-HT uptake was significantly lower in hypothalamus after morphine withdrawal. The possible involvement of the endogenous opioid system in the etiology of the alterations is discussed.
Rönnbäck
L
L
Hansson
E
E
Cupello
A
A
Rapallino
M V
MV
Zeuchner
J
J
Rosengren
L
L
D000284:Administration, Oral; D000818:Animals; D001921:Brain / Q000378:metabolism* / Q000503:physiopathology; D001933:Brain Stem / Q000032:analysis; D002540:Cerebral Cortex / Q000032:analysis; D003342:Corpus Striatum / Q000032:analysis; D006624:Hippocampus / Q000032:analysis; D007031:Hypothalamus / Q000032:analysis; D008297:Male; D009020:Morphine / Q000008:administration & dosage*; D009021:Morphine Dependence / Q000378:metabolism*; D009270:Naloxone / Q000494:pharmacology; D018377:Neurotransmitter Agents / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D005680:gamma-Aminobutyric Acid / Q000378:metabolism
D018377:Neurotransmitter Agents; D009270:Naloxone; D005680:gamma-Aminobutyric Acid; D009020:Morphine