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Effect of Varying the Ionic Concentration of a Microdialysis Perfusate on Basal Striatal Dopamine Levels in Awake Rats
Author(s) -
Osborne P. G.,
O'Connor W. T.,
Ungerstedt U.
Publication year - 1991
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1991.tb08171.x
Subject(s) - microdialysis , dopamine , basal ganglia , basal (medicine) , chemistry , medicine , endocrinology , neuroscience , central nervous system , biology , insulin
In vivo microdialysis was used to study the effects of Ca 2+ , Mg 2+ , and K + ion concentrations on basal extracellular (EC) levels of striatal DA and metabolites in awake rats on the second day (48 h) after implantation of a microdialysis probe. Basal EC striatal dopamine (DA) levels were markedly (90%) and reversibly reduced by removal and subsequent replacement of Ca 2+ ions from the microdialysis perfusate. This implies that the EC DA in this preparation is primarily of synaptic origin. The addition and subsequent removal of 1.7 m M MgCl 2 to the Mg 2+ ‐free perfusate produced a reversible decrease (20%) in basal EC DA levels. This decrease may reflect a competitive interaction between Ca 2+ and Mg 2+ in the process of vesicular release. Basal EC DA levels were also reduced (27%) by decreasing the K + concentration of the perfusate from 4 m M to 3 m M . However, after restoring the K + concentration to 4 m M , EC DA levels were slow to return to pretreatment levels. Basal EC 3,4‐dihydroxyphenylacetic acid and homovanillic acid levels exhibited a parallel but diminished response to each manipulation of the ionic concentration of the perfusate. This study demonstrates that small variations in the concentrations of Ca 2+ , Mg 2+ , and K + in the perfusate employed in microdialysis preparations will affect basal EC striatal DA and metabolite levels.