ISSN:
1573-6903
Keywords:
Cerebral cortex
;
ATP-ases
;
synaptic plasma membranes
;
naloxone
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Abstract Naloxone is a specific competitive antagonist of morphine, acting on opiate receptors, located on neuronal membranes. The effects of in vivo administration of naloxone on energy-consuming non-mitochondrial ATP-ases were studied in two different types of synaptic plasma membranes from rat cerebral cortex, known to contain a high density of opiate receptors. The enzyme activities of Na+, K+-ATP-ase, Ca2+, Mg2+-ATP-ase and Mg2+-ATP-ase and of acetylcholinesterase (AChE) were evaluated on synaptic plasma membranes obtained from control and treated animals with effective dose of naloxone (12μg · kg−1 i.m. 30 minutes). In control (vehicle-treated) animals specific enzyme activities assayed on these two types of synaptic plasma membranes are different, being higher on synaptic plasma membranes of II type than of I type, because the first fraction is more enriched in synaptic plasma membranes. The acute treatment with naloxone produced a significant decrease in Ca2+,Mg2+-ATP-ase activity and an increase in AChE activity, only in synaptic plasma membranes of II type. The decrease of Ca2+,Mg2+-ATP-ase enzymatic activity and the increased AChE activity are related to the interference of the drug on Ca2+ homeostasis in synaptosoplasm, that leads to the activation of calcium-dependent processes, i.e. the extrusion of neurotransmitter. These findings give further evidence that pharmacodynamic characteristics of naloxone are also related to increase [Ca2+] i , interfering with enzyme systems (Ca2+,Mg2+-ATP-ase) and that this drug increases acetylcholine catabolism in synaptic plasma membranes of cerebral cortex.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1023/A:1007529826905
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