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Acute action of rotenone on nigral dopaminergic neurons – involvement of reactive oxygen species and disruption of Ca 2+ homeostasis
Author(s) -
Freestone Peter S.,
Chung Kenny K. H.,
Guatteo Ezia,
Mercuri Nicola B.,
Nicholson Louise F.B.,
Lipski Janusz
Publication year - 2009
Publication title -
european journal of neuroscience
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.346
H-Index - 206
eISSN - 1460-9568
pISSN - 0953-816X
DOI - 10.1111/j.1460-9568.2009.06990.x
Subject(s) - rotenone , pars compacta , trolox , chemistry , substantia nigra , reactive oxygen species , pharmacology , channel blocker , dopaminergic , biophysics , medicine , endocrinology , mitochondrion , biochemistry , calcium , biology , dopamine , oxidative stress , organic chemistry , antioxidant capacity
Rotenone is a toxin used to generate animal models of Parkinson’s disease; however, the mechanisms of toxicity in substantia nigra pars compacta (SNc) neurons have not been well characterized. We have investigated rotenone (0.05–1 μ m ) effects on SNc neurons in acute rat midbrain slices, using whole‐cell patch‐clamp recording combined with microfluorometry. Rotenone evoked a tolbutamide‐sensitive outward current (94 ± 15 pA) associated with increases in intracellular [Ca 2+ ] ([Ca 2+ ] i ) (73.8 ± 7.7 n m ) and intracellular [Na + ] (3.1 ± 0.6 m m ) (all with 1 μ m ). The outward current was not affected by a high ATP level (10 m m ) in the patch pipette but was decreased by Trolox. The [Ca 2+ ] i rise was abolished by removing extracellular Ca 2+ , and attenuated by Trolox and a transient receptor potential M2 (TRPM2) channel blocker, N ‐( p ‐amylcinnamoyl) anthranilic acid. Other effects included mitochondrial depolarization (rhodamine‐123) and increased mitochondrial reactive oxygen species (ROS) production (MitoSox), which was also abolished by Trolox. A low concentration of rotenone (5 n m ) that, by itself, did not evoke a [Ca 2+ ] i rise resulted in a large (46.6 ± 25.3 n m ) Ca 2+ response when baseline [Ca 2+ ] i was increased by a ‘priming’ protocol that activated voltage‐gated Ca 2+ channels. There was also a positive correlation between ‘naturally’ occurring variations in baseline [Ca 2+ ] i and the rotenone‐induced [Ca 2+ ] i rise. This correlation was not seen in non‐dopaminergic neurons of the substantia nigra pars reticulata (SNr). Our results show that mitochondrial ROS production is a key element in the effect of rotenone on ATP‐gated K + channels and TRPM2‐like channels in SNc neurons, and demonstrate, in these neurons (but not in the SNr), a large potentiation of rotenone‐induced [Ca 2+ ] i rise by a small increase in baseline [Ca 2+ ] i .