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Selective and Nonselective Effects of 1‐Methyl‐4‐ Phenylpyridinium on Oxygen Consumption in Rat Striatal and Hippocampal Slices
Author(s) -
Martin Frederick R.,
SanchezRamos Juan,
Rosenthal Myron
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.tb08299.x
Subject(s) - mptp , chemistry , mazindol , dopaminergic , hippocampal formation , extracellular , dopamine , biophysics , oxygen , striatum , neurotoxin , neurotoxicity , biochemistry , medicine , neuroscience , pharmacology , biology , toxicity , organic chemistry
Insights into the etiology and pathophysiology of Parkinson's disease may derive from elucidation of the neurotoxic mechanisms of 1‐methyl‐4‐phenyl‐1, 2, 3, 6‐tetrahydropyridine (MPTP) and its active metabolite, I‐methyl‐4‐phenylpyridinium (MPP + ). In previous studies, MPP + provoked oxidation of cytochrome b and K + leakage into the extracellular space of rat striatal slices. Magnitudes of these time‐dependent responses were far greater than expected had the MPP + effects been limited to dopaminergic terminals. To determine whether cytochromes become oxidized from K + ‐induced increases in ion transport activity or from electron transport inhibition at complex I, oxygen consumption was measured because this should be increased by the former and decreased by the latter mechanism. Low MPP + concentrations (1 μ M ) decreased O 2 consumption (∼40% in 3 h) in striatal slices. This decrease was diminished by mazindol and did not occur in hippocampal slices. High toxin concentrations (100 μ M ) inhibited oxygen consumption to a greater extent (∼60%) in striatal slices; this inhibition was still greater in hippocampal slices. These results support the hypothesis that acute effects of low (“selective”) MPP + concentrations require the presence of dopaminergic terminals to trigger a sequence of destructive metabolic events but that the metabolic consequences of MPP + spread to neighboring cells. In contrast, high MPP + concentrations nonselectively inhibit metabolic and ion transport activity without requiring the presence of dopaminergic terminals. These results also suggest that physiological effects of “selective” MPP + concentrations extend to nondopaminergic cells.