Acute action of rotenone on nigral dopaminergic neurons--involvement of reactive oxygen species and disruption of Ca2+ homeostasis

Abstract 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 lm) 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 [Ca2+] ([Ca2+]i) (73.8 ± 7.7 nm) and intracellular [Na+] (3.1 ± 0.6 mm) (all with 1 lm). The outward current was not affected by a high ATP level (10 mm) in the patch pipette but was decreased by Trolox. The [Ca2+]i rise was abolished by removing extracellular Ca2+, 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 nm) that, by itself, did not evoke a [Ca2+]i rise resulted in a large (46.6 ± 25.3 nm) Ca2+ response when baseline [Ca2+]i was increased by a ‘priming’ protocol that activated voltage-gated Ca2+ channels. There was also a positive correlation between ‘naturally’ occurring variations in baseline [Ca2+]i and the rotenone-induced [Ca2+]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 [Ca2+]i rise by a small increase in baseline [Ca2+]i

Properties of dopaminergic neurons in organotypic mesencephalic-striatal co-cultures--evidence for a facilitatory effect of dopamine on the glutamatergic input mediated by α-1 adrenergic receptors.

Organotypic cultures (OCs) have been widely used to investigate the midbrain dopaminergic system, but only a few studies focused on the functional properties of dopaminergic neurons and their synaptic inputs from dopaminergic and non-dopaminergic neuronsalso contained in such cultures. In addition, it is not clear whether the culturing process affects the intrinsic neuronal properties and the expression of specific receptors and transporters. We performed patch-clamp recordings from dopaminergic neurons in mesencephalic–striatal co-cultures obtained from transgenic mice expressing green fluorescent protein (GFP) under the tyrosine hydroxylase promoter. Some (10 ⁄ 44) GFP+ neurons displayed a bursting activity that renders the firing of these cells similar to that of the dopaminergic neurons in vivo. The culturing process reduced the hyperpolarization-activated current (Ih) and the expression of D2 receptors. Downregulation of D2 receptor mRNA and protein was confirmed with reverse transcriptase polymerase chain reaction and Western blotting. Immunocytochemistry revealed that many synaptic terminals, most likely originating from dopaminergic neurons, co-expressed the dopamine (DA) transporter and the vesicular glutamate transporter-2, suggesting a co-release of DA and glutamate. Interestingly, exogenous DA decreased glutamate release in young cultures [days in vitro (DIV) < 20] by acting on pre-synaptic D2 receptors, while in older cultures (DIV > 26) DA increased glutamate release by acting on a-1 adrenoreceptors. The facilitatory effect of DA on glutamatergic transmission to midbrain dopaminergic neurons may be important in conditions when the expression of D2 receptors is compromised, such as long-term treatment with antipsychotic drugs. Our data show that midbrain OCs at DIV > 26 may provide a suitable model of such condition

Properties of dopaminergic neurons in organotypic mesencephalic-striatal co-cultures--evidence for a facilitatory effect of dopamine on the glutamatergic input mediated by \u3b1-1 adrenergic receptors.

Organotypic cultures (OCs) have been widely used to investigate the midbrain dopaminergic system, but only a few studies focused on the functional properties of dopaminergic neurons and their synaptic inputs from dopaminergic and non-dopaminergic neurons also contained in such cultures. In addition, it is not clear whether the culturing process affects the intrinsic neuronal properties and the expression of specific receptors and transporters. We performed patch-clamp recordings from dopaminergic neurons in mesencephalic-striatal co-cultures obtained from transgenic mice expressing green fluorescent protein (GFP) under the tyrosine hydroxylase promoter. Some (10/44) GFP+ neurons displayed a bursting activity that renders the firing of these cells similar to that of the dopaminergic neurons in vivo. The culturing process reduced the hyperpolarization-activated current (I(h) ) and the expression of D\u2082 receptors. Downregulation of D\u2082 receptor mRNA and protein was confirmed with reverse transcriptase polymerase chain reaction and Western blotting. Immunocytochemistry revealed that many synaptic terminals, most likely originating from dopaminergic neurons, co-expressed the dopamine (DA) transporter and the vesicular glutamate transporter-2, suggesting a co-release of DA and glutamate. Interestingly, exogenous DA decreased glutamate release in young cultures [days in vitro (DIV)<20] by acting on pre-synaptic D\u2082 receptors, while in older cultures (DIV>26) DA increased glutamate release by acting on \u3b1-1 adrenoreceptors. The facilitatory effect of DA on glutamatergic transmission to midbrain dopaminergic neurons may be important in conditions when the expression of D\u2082 receptors is compromised, such as long-term treatment with antipsychotic drugs. Our data show that midbrain OCs at DIV>26 may provide a suitable model of such conditions

Physicians' knowledge and continuing medical education regarding fitness to drive: a questionnaire-based survey in Southeast Switzerland

Valid information for physicians in Switzerland concerning knowledge and continuing education in traffic medicine is not available. Also, their attitude to the legally prescribed periodic driving fitness examinations is unclear. In order to gain more information about these topics, 635 resident physicians in Southeast Switzerland were sent a questionnaire (response rate 52%). In a self-estimation, 79% of the queried physicians claimed to know the minimal medical requirements for drivers which are important in their specialty. Statistically significant differences existed between the specialties, whereby general practitioners most frequently claimed to know the minimal medical requirements (90%). It appears that the minimal medical requirements for drivers are well known to the queried physicians. Fifty-two percent of the physicians favored an expansion of continuing education in traffic medicine. Such an expansion was desired to a lesser extent by physicians without knowledge of the minimal requirements (p < 0.001). A clear majority of the medical professionals adjudged the legally prescribed periodic driving fitness examinations as being an expedient means to identify unfit drivers. A national standardized form for reporting potentially unfit drivers to the licensing authorities was supported by 68% of the responding physicians. Such a form could simplify and standardize the reports to the licensing authorities

Structural, functional and molecular analysis of the effects of aging in the small intestine and colon of C57BL/6J mice

Contains fulltext : 109613.pdf (publisher's version ) (Open Access)BACKGROUND: By regulating digestion and absorption of nutrients and providing a barrier against the external environment the intestine provides a crucial contribution to the maintenance of health. To what extent aging-related changes in the intestinal system contribute to the functional decline associated with aging is still under debate. METHODS: Young (4 M) and old (21 M) male C57BL/6J mice were fed a control low-fat (10E%) or a high-fat diet (45E%) for 2 weeks. During the intervention gross energy intake and energy excretion in the feces were measured. After sacrifice the small and large intestine were isolated and the small intestine was divided in three equal parts. Swiss rolls were prepared of each of the isolated segments for histological analysis and the luminal content was isolated to examine alterations in the microflora with 16S rRNA Q-PCR. Furthermore, mucosal scrapings were isolated from each segment to determine differential gene expression by microarray analysis and global DNA methylation by pyrosequencing. RESULTS: Digestible energy intake was similar between the two age groups on both the control and the high-fat diet. Microarray analysis on RNA from intestinal scrapings showed no marked changes in expression of genes involved in metabolic processes. Decreased expression of Cubilin was observed in the intestine of 21-month-old mice, which might contribute to aging-induced vitamin B12 deficiency. Furthermore, microarray data analysis revealed enhanced expression of a large number of genes involved in immune response and inflammation in the colon, but not in the small intestine of the 21-month-old mice. Aging-induced global hypomethylation was observed in the colon and the distal part of the small intestine, but not in the first two sections of the small intestine. CONCLUSION: In 21-month old mice the most pronounced effects of aging were observed in the colon, whereas very few changes were observed in the small intestine