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Olfaction 1 Odor as a stimulus Olfactory receptors: Structure and function Antennal lobe: coding odors at the level of the primary olfactory neuropil Natural odors are composed of many molecular components Which all have their own characteristic smell. The mixture of all the components usually smell very different from that of any compenent. The smell of any component or mixture can depend very much on the concentration. Gaschromatigraph of odor natural mixtures Roman Kaiser, Vom Duft der Orchideen, 1993 Natürliche Düfte sind Gemische, deren Zusammensetzung sich ändern kann Duft der Orchidee Angraecum sesquipedale in der ersten und der zweiten Nacht des Blühens Roman Kaiser, Vom Duft der Orchideen, 1993 Substanzen, die den Jasminduft prägen Mori and Yoshihara, 1995 Duftcharaktere aber: stark von der Konzentration abhängig. z.B. Ionon (in Parfums enthalten: niedrige Konzentration: Veilchenduft hohe Konzentration: Holzduft Roman Kaiser, 1993 - Odor character - Odor concentration - Temporal structure -Dependence on wind direction - Mixture effects - Hedonic There are two olfactory systems in all animals -The pheromone system -The general odor system For example in mammals: Pheromone system: vomero-nasal organ (VNO) Axons of the olfactory neruons projects to the accessory olfactory bulb (AOB) For general odors: main olfactory epithelium Axons of the olfactory neurons project to the Olfactory bulb However. these two systems are often not fully separated in function Belluscio et al. 1999 Das Riechepithel von Säugetieren Duft Duftmoleküle Mukus Zilien der ORZ Riechepithel mit ORZ Cilien Mukus Rezeptoraxone Olfaktorische Rezeptorzelle (ORZ) Soma der ORZ Zilie der ORZ Wahrnehmung von allgemeinen Düften Olfaktorischer Bulbus Axone der Mitralzellen Odor receptor molecules are G-protein coupled receptors bei Säugern gibt es mehr als 1000 Gene für Duftrezeptoren bei Drosophila ca 50 Duftrezeptoren in der Säugetiernase 7 Membran schleifen Two second messenger pathways are involved in the transduction processes Hill, Wyse, Anderson Animal Physiology, Sinauer, 2004 Olfactory sensillae in insects Antenna of the bee Scapus Pedicellus Flagellum Pore plates Sensillum placodium Lacher, 1964 v. Frisch 1965, p. 509 Extracellular recordings from placode sensilla Two different Placode sensilla (A,B) Akers and Getz, Chem. Senses 1992 Response spectra of different classes of olfactory receptor cells on the bee antenna E. Vareschi, Z. vergly. Physiol. 75, 143-173, 1971 The Nose of a fly de Bruyne 2001 Olfactory sensillae in flies de Bruyne 1999 ORNs can be grouped in classes de Bruyne 1999 There are many different ORN classes Distribution of sensillum types on antenna 22 ORN classes in 9 types of sensilla de Bruyne 2001 The expression pattern of olfactory Receptor genes in Drosophila shows: -different receptor molecules are expressed in different receptor neurons -axones of recept neurons project to the same glomerulus Or 22a Antennal Lobus Vosshall et al. 1999 Coding general odors in the honey bee Glomeruli Antennal lobe Antennal nerve: axons of olfactory receptor cells Nelken Duft Oktanol Odors are coded at the level of the antennal lobe (and the olfactory bulb) in a combinatorial pattern of overlapping glomerular activities. Aliphatic alcohols of different carbon chain length Antagonistic components shape odor coding Odor stimulation leads to both excitatory and inhibitory activity In different glomeruli QuickTime™ and a decompressor are needed to see this picture. 1-Octanol repetative stimulation Antennal lobe of the bee Odor induced Ca signals What do these effects implicate for the AL-network? PTX Ringer homomeric LI (GABA-IR) His ? GABA Silke Sachse, Giovanni Galicia Odor specific patterns correlate less in PN measurements -0.10 0.70 -0.12 0.53 0.93 0.31 Retina Die inhibitorische Verschaltung im olfakt. Bulbus/Antennallobus gleicht der in der Retina: es gibt zwei Ebenen der inhibitorischen lateralen Verschaltung Rezeptoraxone von anderen Olfaktor. Bulbus Glomeruli zu anderen Glomeruli inhibitorische Neurone Projektionsneurone aus Squire et al. Abb. 24.19 The calyces of the mb are organized according to sensory modalities olfactory input lip: olfactory visual input basal ring: mixed collar: visual gustatory input Schroeter and Menzel 03 Kirschner et al. 06 Wulfila Gronenburg Ca2+ Imaging PNs and Kenyon cells raw fluorescnece images selective staining of PNs and KCs KC dendrites KC somata Mushroom body PN boutons KC PN Antennal lobe sites of dye injection (Fura 2 dextran) PN min DF/F max glomeruli odor induced KC signal Odors evoke patterns of activity increase and decrease at the input to the mushroom body Nobu Yamagada, unpubl. 07 Odor specific combinatorial codes at three levels 1-hexanol limonen linalool 2-octanol max DF/F Kenyon cells lio min PN boutons lio PN dendrites Paul Szyszka et al. 2005 averages of 3 stimulations Kenyon cells respond only transiently to odors (sparse time code) clawed Kenyon cell PN boutons projection neuron mean KC and PN responses 3s 1-hexanol odor + DF/F P. Szyska et al. 2005 . Sparsening of the combinatorial population codes at three levels of olfactory integration Kenyon cells lio 1-hexanol A small proportion of the clawed Kenyon cells respond (1%). somata neuropil PN boutons lio - DF/F neuropil + PN dendrites P. Szyska et al. 2005 max min Boutons of projection neurons show excitatory and inhibitory responses. The postsynaptic sides of glomeruli (projection neurons) show excitatory and inhibitory responses. A large proportion respond: 25% Organization of the microglomerulus Jürgen Rybak KN KN DG PN inh N KN microglomerulus modulatory input, VUMmx1 Dirk Müller Olga Ganeshina Model of odor processing in the MB lip odor Mushroom body local inhibition + Antennal lobe + + + + - +-+ - PN integration whithin 200 ms delayed inhibition release from inhibition KC • transformation of the complex temporal PN response into a binary Kenyon cell response microcircuit of the lip Ganeshina, Menzel J. comp. Neurol. 2001 KC PN exc. PN inh. Paul Szyska et al. 2005 Morphological networks: Olfactory interneurons Registration of 2 projection neurons und 1 local interneurons in the standard atlas of the bee brain Projection neurons recording site FUA: few unit activity 110 “units”, 18% single units, 82% 2-3 units Rate response changes in the course of conditioning About equal numbers of FUAs increased and decreased rate responses (+/- stanfard deviation) More for CS+ than for CS- and Ctr. Out of 110 FUAs: 13 switched responses (mostly for CS+); 3 were recruited t o CS+, 2 did not respond to CS+ any more after conditioning. PCA of rate responses and hierarchical cluster analysis (ensemble activity) starting from a 110 dimensional space Ctr CS+ CS- First 3 PCs: 83% variance. No difference if only the behavioral learners are analyzed LFP changes in the course of conditioning (average of the 3 trials per animal, normalized to unit area) error bars +/- 95% (boot-strap Procedure)