par- 12 mars 2013
Olfaction : du Codage à la Mémoire
Influence de l’apprentissage
et du métabolisme sur le réseau olfactif
PhD, Associate Professor
Learning and metabolism modulate the olfactory network
Using in vitro electrophysiological recordings performed on brain slice and acute explants I sight to further the understanding of some of the neural processes taking place in the first two stages of the olfactory system i.e. the olfactory mucosa and the olfactory bulb during modulation by :
In the piriform cortex, it is known that the acquisition of the rules to perform an olfactory discrimination task is correlated with a modulation of pyramidal neurons excitability (Saar et Barkai, 2009, Mol Neurobiol. 39(3):171). The olfatory bulb is also implicated in learning memory but the related modification in neuronal excitability have to be studied. Using electrophysiological patch clamp recordings we characterized the electrical properties of the mitral cells i- in control rats ; ii-in rats trained to perceive an odor ; iii- in rats trained to realized an olfactory discrimination task.
At the peripheral level, in collaboration with Minghong Ma and Xavier Grosmaitre (University of Pennsylvania, USA), we studied the effects of insulin and leptin perfusion on the functional properties of olfactory sensory neurons (OSNs) (Savigner et al., 2009). We analyzed the spontaneous activity of rat OSNs in an in vitro intact epithelium preparation. Bath perfusion of insulin and leptin enhanced the electrical excitability of OSNs while, surprisingly, they reduced their odorant-induced activity when measured in global electroolfactogram and at individual cells level. These results suggest that insulin and leptin may decrease the global signal to noise ratio of the olfactory epithelium in responding to odors and thus modulate the performance of the system in order to matches the smell ability to the satiety status. At the olfactory bulb level, on the bulbar network we conducted patch-clamp recordings on olfactory bulb slices to investigate how insulin or leptin modulate the excitability of the mitral cells (the main output neurons of the OB,). Current-clamp experiments show that insulin perfusion mainly increases the spontaneous firing frequency of MCs. Voltage-clamp recordings in pharmacologically isolated cells show that insulin reduces two potassium conductances : IA and IKDR. These data suggest that the insulin-induced increase in MC firing frequency by acting on various potassic currents. Technical experiences : Whole cell and perforated patch-clamp recording techniques, In vivo unitary extracellular recordings, Pharmacology, Ion channel modulation, Accreditation for live animals experimenting, Cell culture, Immunocyto- and histochemistry. Measurement of acetylcholine by chemiluminescence.