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Section MOLECULAR NEUROSCIENCE
Rodents and Humans are Able to Discriminate the Odour of L-Lactate
Valentina Mosienko*, Anja Teschemacher, Sergey Kasparov
University of Bristol, Biomedical Sciences, School of Physiology, Pharmacology and Neuroscience, UK. * Presenting e-mail: [email protected]
Olfactory receptors (Olfrs) are seven transmembrane G-protein coupled receptors that are able to sense odorants. Rodents express over 1000 olfactory receptors while in humans only less than 400 of these genes are active. Some of the olfactory receptors are expressed not only in olfactory epithelium but in other tissues. One such receptor is mouse Olfr78 which has a rat and human orthologs (Orl59, OR51E2, correspondingly). Olfr78 has been implicated in various physiological processes due to its ectopic expression outside the olfactory system in other parts of the brain (brainstem, area postrema, nucleus tractus solitarius) and peripheral tissues (carotid body, prostate gland, kidney). It is activated by short chain fatty amino acids acetate and propionate, but also by L-lactate. Given that Olfr78 is specifically expressed in olfactory sensory neurons, we hypothesized that both rodents and humans should be able to smell lactate. To test this hypothesis we performed olfactory discrimination tasks with mice, rats and humans.
Our results show that adult male C57Bl/6 mice are able to distinguish L-lactate (1M, pH=7.4) in olfactory habitua-tion-dishabituation and discrimination tasks. Mice spend twice as much time sniffing L-lactate compared to water, and equal amounts of time sniffing peppermint extract. Upon multiple exposures, mice habituate to the smell of L-lactate, however, they clearly discriminate the next introduced odour as measured by increased sniffing time.
We also used an operant-conditioning task reinforced by food to test the ability of rats to distinguish L-lactate (1M, pH=7.4). Rats were kept to a diet to maintain 85% of their free body weight and trained to find a food reward guided by the smell of either almond (positive control) or L-lactate. Rats were offered three sponges in an arena, where only one was marked with an odorant and contained a food reward. Success in finding a food reward orienting on the smell was measured by the time elapsed until food retrieval. Both almond and L-lactate odour were equally effective as operant stimuli as rats spent the same amount of time to find and retrieve the food reward upon exposure and this latency to food retrieval decreased over trials for both odours. We observed no difference in accuracy (number of incorrect pokes into sponge probes) over all trials between almond and L-lactate.
In order to test whether humans can sense L-lactate we recruited young adult volunteers for an odorant discrimination task. Participants were asked to indicate a presence of smell in four jars containing liquids (1M acetate, propionate, pyruvate and L-lactate adjusted to pH 7.4). Distilled water served as a negative control. 99% of participants indicated the presence of smell for a solution containing propionate, 97% and 95% detected an odour in solutions of pyruvate or acetate, respectively. 93% of participants detected an odour in a solution containing L-lactate. All the participants were asked to rate all samples in dimensions of taste and odour. 34% of participants identified the smell of l-lactate as sweet and 19% described it as sour/acidic. Altogether, our data demonstrate that both rodents and humans are able to sense L-lactate, most likely via Olfr78 (or its ortholog). The biological significance of L-lactate detection by olfaction requires further investigation.
Calcineurin Inhibition Attenuates Function of the Neuronal Potassium-Chloride Cotransporter
Michael Zessin1, Christin Boldt1, Rudolf Deisz1, Ulf Strauß1, Sebastian Loyola1, Aljona Borschewski1, Jim McCormick2, and Kerim Mutig1*
1 Department of Anatomy, CharM-Universitätsmedizin Berlin, Germany;
2 Division of Nephrology and Hypertension, Oregon Health and Science University, Portland, Oregon, USA. * Presenting e-mail: [email protected]
Aims
Calcineurin inhibitors, cyclosporine and tacrolimus, are broadly used for immunosuppression after organ transplantations but may cause serious neurologic side effects such as tremor, ataxia, or seizures suggesting that these drugs may induce hyperexdtability of neocortical neurons. Calcineurin has been implicated in the regulation of neuronal excitability and cellular chloride homeostasis. In this context, we tested the hypothesis that calcineurin inhibitors interfere with the function of major neuronal cation-chloride cotransporter KCC2.
OM&P
Section MOLECULAR NEUROSCIENCE Methods
To study effects of calcineurin inhibition on the KCC2 activity cyclosporine was applied in vivo or in rat brain slices. The evaluations were performed using immunofluorescence, immunoblotting and co-immunoprecipitation, quantitative PCR, and electrophysiological measurements with sharp microelectrode.
Results
Calcineurin and KCC2 co-localized in rat neocortical neurons by immunofluorescence and interacted by co-immuno-precipitation. Short term administration of cyclosporine to rats (25 mg/kg for 1 to 4h) resulted in increased tyrosine phosphorylation of KCC2 suggesting inhibition of its activity. In line with this, intracellular recordings of chloride homeostasis after iontophoretic Cl- loading revealed strong cyclosporine-induced prolongation of the Cl- extrusion time (+3.4s, p<0.05) which was compatible with KCC2 blockade. Chronic administration of cyclosporine to rats (5 to 25 mg/kg for 14 days) drastically reduced the level of activating KCC2 phosphorylation at S940 (-65%, p<0.05). In addition, expression of the KCC2-inhibiting SPAK kinase was significantly increased upon chronic cyclosporine treatment (+59%, p<0.05).
Conclusions
In summary, our data suggest that calcineurin inhibition using cyclosporine attenuates KCC2 function in acute and chronic settings. Our data have clinical implications for immunosuppressive therapy using calcineurin inhibitors.
Lack of Diap3 Relaxes the Spindle Checkpoint Causing the Loss of Neural Progenitors and Microcephaly
Fadel Tissir*
University of Louvain, Belgium. * Presenting e-mail: [email protected]
The diaphanous homologue Diap3 (also referred to as mDia2, DIAPH3 in humans) is a major regulator of actin dynamics. Loss of Diap3 has been constantly associated with cytokinesis failure ascribed to impaired accumulation of F-actin in the cleavage furrow. We provide evdence that Diap3 is required prior to cell fission to ensure the accurate segregation of chromosomes. In mice, inactivation of the Diap3 gene causes a massive loss of neural progenitor cells with subsequent reduction in the number of intermediate progenitors and neurons, and ultimately results in microcephaly. Mechanistically, we show that Diap3 co-localises with chromosomal passenger complex (CPC) proteins at the kinetochore-mitotic spindle interface, and interacts physically with BubRl and Survivin, components of the spindle assembly checkpoint (SAC) and CPC respectively. Diap3-deficient neural progenitor cells have decreased levels of BubRl, and fail to properly distribute CPC proteins, or activate the SAC. Hence, they bypass the mitotic arrest and embark on anaphase in spite of incorrect chromosome segregation which causes their apoptotic death. These findings identify Diap3 as an important guard of cortical progenitors, shed new light on the mechanisms of action of Diaphanous formins during cell division, and add insights into the pathobiology of primary microcephaly
Sip 1-Mutahon Causes a Disturbance in Activity of NMDA- and AMPA-Receptors of Neurons in Cerebral Cortex
M.V. Turovskaya*, A.A. Babaev, E.A. Turovsky, V.S. Tarabykin
Institute of Biology and Biomedicine, Lobachevsky State University of Nizhny Novgorod. * Presenting e-mail: [email protected]
OM&P
