Olfaction 1 Odor as a stimulus Olfactory receptors: Structure and function Antennal lobe: coding odors at the level of the primary olfactory neuropil

on the concentration. 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 Squire Abb. 24.14 Moleküle im Jasminduft Mori and Yoshihara, 1995

Duftcharaktere aber: stark von der Konzentration abhängig. z.B. Roman Kaiser, 1993 aber: stark von der Konzentration abhängig. z.B. Ionon (in Parfums enthalten: niedrige Konzentration: Veilchenduft hohe Konzentration: Holzduft Duftcharaktere

- 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 Rodriguez et al 1999 Vomeronasalorgan Rezeptor Gege siehe Abb. RezeptorGene.ppt dort Text However. these two systems are often not fully separated in function Belluscio et al. 1999

Das Riechepithel von Säugetieren Olfaktorische Rezeptorzelle (ORZ) Soma der ORZ Zilie der ORZ Mukus Duft Duftmoleküle Mukus Zilien der ORZ Riechepithel mit ORZ Cilien Rezeptoraxone Olfaktorischer Bulbus Axone der Mitralzellen Wahrnehmung von allgemeinen Düften

Duftrezeptoren in der Säugetiernase 7 Membran schleifen Odor receptor molecules are G-protein coupled receptors bei Säugern gibt es mehr als 1000 Gene für Duftrezeptoren bei Drosophila ca 50

Two second messenger pathways are involved in the transduction processes Hill, Wyse, Anderson Animal Physiology, Sinauer, 2004

Nature 413, 211ff, 2001

Olfactory sensillae in insects Axel 1995

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 Sensillum types as shown in pheromone talk. Detailed knowledge available for the basiconic type (they make up about half of all input to the brain) de Bruyne 2001

Olfactory sensillae in flies Singel sensillujm electrophysiology shows two cells per sensillum. They can be separately analysed because of spike shape differences. In each sensillum the two cells have a different response spectrum de Bruyne 1999

ORNs can be grouped in classes Recording from many individual basiconic sensilla. They can be classified via a hierarchical clustering procedure and the data show they fall into response classes. de Bruyne 1999

There are many different ORN classes Distribution of sensillum types on antenna 22 ORN classes in 9 types of sensilla Overview of present knowledge on ORN (olfactory receptor neuron) response classes. The are distributed on the two organs (antenna and palp) and on the antenna in partly overlapping zones. de Bruyne 2001

Verschiedene Rezeptoren auf der Antenne Or 22a 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 Vosshall et al. 1999 Verschiedene Rezeptoren auf der Antenne Antennal Lobus Cell, Vol. 96, 725-736, March 5,1999, Copyright ©1999 by Cell Press A Spatial Map of Olfactory Receptor Expressionin the Drosophila Antenna Leslie B. Vosshall,* Hubert Amrein,*Pavel S. Morozov.t Andrey Rzhetsky.tand Richard Axel** . Department of Biochemistry and Molecular BiophysicsHoward Hughes Medical Institutet Columbia Genome CenterColumbia University College of Physicians and Surgeons New York, New York 10032Summary Insects provide an attractive System for the study olfactory sensory perception. We have identified a novel family of seven transmembrane domain proteins, en-coded by 100 to 200 genes, that is likely to represent the family of Drosophila odorant receptors. Members of this gene family are expressed in topographically defined subpopulations of olfactory sensory neurons in either the antenna or the maxillary palp. Sensory neurons express different complements of receptor qenes, such that individual neurons are functionally distinct. The isolation of candidate odorant receptor genes along with a genetic analysis of olfactory-dnven behavior in insects may ultimately afford a system to understand the mechanistic link between odor recog- nition and behavior.

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 1-Octanol repetative stimulation Antennal lobe of the bee Odor induced Ca signals

What do these effects implicate for the AL-network? Ringer PTX ? GABA homomeric LI (GABA-IR) His Silke Vortrag Göttigen 01 Silke Sachse, Giovanni Galicia

Silke Vortrag Göttigen 01 Odor specific patterns correlate less in PN measurements -0.10 -0.12 0.70 0.53 0.31 0.93 Silke Vortrag Göttigen 01

Die inhibitorische Verschaltung im olfakt. Bulbus/Antennallobus gleicht der in der Retina: es gibt zwei Ebenen der inhibitorischen lateralen Verschaltung Retina 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 collar: visual basal ring: mixed visual input gustatory input Schroeter and Menzel 03 Kirschner et al. 06 Wulfila Gronenburg

Ca2+ Imaging PNs and Kenyon cells raw fluorescnece images odor induced KC signal selective staining of PNs and KCs KC dendrites KC somata Mushroom body PN boutons KC PN Antennal lobe KC boutons and KC somata 5µm in diameter imaging with high resolution 11017a whole brain, PN 60x 20726a KC 040202b, AL AL PN groupped into funktional subunit with same receptive fields PNs project to the MB lip where they mak sites of dye injection (Fura 2 dextran) PN glomeruli min DF/F max

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 Kenyon cells 1-hexanol limonen linalool 2-octanol lio max min DF/F PN boutons lio 10823a pn Traces OC2, hx1 Roi 38 PN dendrites averages of 3 stimulations Paul Szyszka et al. 2005

Kenyon cells respond only transiently to odors (sparse time code) clawed Kenyon cell mean KC and PN responses PN boutons projection neuron 3 s 10823a 1-hexanol DF/F + odor P. Szyska et al. 2005 .

Sparsening of the combinatorial population codes at three levels of olfactory integration 1-hexanol lio Kenyon cells PN boutons PN dendrites neuropil somata max min A small proportion of the clawed Kenyon cells respond (1%). Boutons of projection neurons show excitatory and inhibitory responses. DF/F + KC 10803b Boutons 10829a Glom 040402b The postsynaptic sides of glomeruli (projection neurons) show excitatory and inhibitory responses. A large proportion respond: 25% - P. Szyska et al. 2005

Organization of the micro- glomerulus microglomerulus KN DG inh PN N Jürgen Rybak inh N PN KN DG microglomerulus modulatory input, VUMmx1 Olga Ganeshina Dirk Müller

Model of odor processing in the MB lip Mushroom body local inhibition + - + - - PN - - - + - - + + + + Antennal lobe integration whithin 200 ms delayed inhibition release from inhibition KC transformation of the complex temporal PN response into a binary Kenyon cell response KC PN exc. PN inh. microcircuit of the lip Ganeshina, Menzel J. comp. Neurol. 2001 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 FUA: few unit activity 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)