The spontaneous release of acetylcholinesterase in rat substantia nigra is altered by local changes in extracellular levels of dopamine.
Acetylcholinesterase release in the guinea-pig substantia nigra has been previously investigated 'on-line', using a sensitive chemiluminescent system. Since histological observations suggest that there is a difference in acetylcholinesterase distribution in the rat substantia nigra compared to that of the guinea-pig, the first aim of the present study was to use this chemiluminescent method to characterise acetylcholinesterase release in this brain region of the freely moving rat, and the second was explore the relationship between acetylcholinesterase release and dopamine systems in this region. Accordingly, acetylcholinesterase release in the rat substantia nigra was studied under basal conditions of spontaneous release and following the local administration of (a) elevated potassium ions (30, 45, 60'mM), (b) a stimulator of dopamine/acetylcholinesterase release-D-amphetamine (10(-7), 10(-6) and 10(-5) M), (c) an inhibitor of dopamine uptake-GBR12909 (10(-7), 10(-6) and 10(-5) M). Spontaneous release of acetylcholinesterase in this brain region of the rat appears to be comparable with that observed in the guinea-pig, despite the smaller number of acetylcholinesterase-containing neurones. Furthermore, not only elevated potassium ions, but D-amphetamine as well as GBR12909, all produced significant increases in the percentage spontaneous release of acetylcholinesterase. Thus, the release of acetylcholinesterase in this region may be triggered by levels of dopamine outside of the neurone.
Dally
J J
JJ
University Department of Pharmacology, Oxford, U.K.
Schaefer
M
M
Greenfield
S A
SA
D000110:Acetylcholinesterase / Q000378:metabolism*; D000818:Animals; D003913:Dextroamphetamine / Q000494:pharmacology; D004298:Dopamine / Q000378:metabolism*; D018765:Dopamine Uptake Inhibitors / Q000494:pharmacology; D004353:Drug Evaluation, Preclinical; D008163:Luminescent Measurements; D008297:Male; D010879:Piperazines / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology*; D051381:Rats; D013045:Species Specificity; D013378:Substantia Nigra / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism
D018765:Dopamine Uptake Inhibitors; D010879:Piperazines; C043425:vanoxerine; D000110:Acetylcholinesterase; D011188:Potassium; D003913:Dextroamphetamine; D004298:Dopamine