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 componentsWhich all have their own characteristic smell.The mixture of all the componentsusually smell very different fromthat of any compenent.

The smell of any component ormixture can depend very much on the concentration.

Roman Kaiser, Vom Duft der Orchideen, 1993

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

Mori and Yoshihara, 1995

Substanzen, die den Jasminduft prägen

Roman Kaiser, 1993

aber:stark von der Konzentration abhängig.

z.B.Ionon (in Parfums enthalten:niedrige Konzentration: Veilchendufthohe Konzentration: Holzduft

Duftcharaktere

- Odor character- Odor concentration- Temporal structure-Dependence on wind direction- Mixture effects- Hedonic

There are two olfactory systems in all animals

Belluscio et al. 1999

-The pheromone system-The general odor system

However.these two systems are often not fullyseparated in function

For example in mammals:Pheromone system: vomero-nasal organ (VNO)Axons of the olfactory neruons projectsto the accessory olfactory bulb (AOB)

For general odors: main olfactory epitheliumAxons of the olfactory neurons project to theOlfactory bulb

Rezeptoraxone

Riechepithelmit ORZ

Duft

Mukus

Zilien derORZ

OlfaktorischerBulbus

Axone der Mitralzellen

Das Riechepithel von Säugetieren

OlfaktorischeRezeptorzelle(ORZ)

Soma derORZ

Zilie der ORZ

Mukus

Wahrnehmung von allgemeinen Düften

Cilien

Duftmoleküle

Duftrezeptoren in der Säugetiernase

7 Membran schleifen

Odor receptor molecules are G-protein coupled receptors

bei Säugern gibt es mehr als 1000 Genefür Duftrezeptorenbei Drosophilaca 50

Hill, Wyse, Anderson Animal Physiology, Sinauer, 2004

Two second messenger pathways are involved in the transduction processes

Olfactory sensillae in insects

v. Frisch 1965, p. 509

Antenna of the beeScapus

Pedicellus

Flagellum

Pore platesSensillum placodium

Lacher, 1964

Two different Placode sensilla (A,B)

Akers and Getz, Chem. Senses 1992

Extracellular recordings from placode sensilla

E. Vareschi, Z. vergly. Physiol. 75, 143-173, 1971

Response spectra of differentclasses of olfactory receptorcells on the bee antenna

The Nose of a fly

de Bruyne 2001

de Bruyne 1999

Olfactory sensillae in flies

ORNs can be grouped in classes

de Bruyne 1999

There are many different ORN classes

de Bruyne 2001

22 ORN classes in 9 types of sensilla

Distribution of sensillum types on antenna

Or 22a

The expression pattern of olfactoryReceptor 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

AntennalLobus

Coding general odors in the honey bee

Antennal lobe

Antennal nerve: axons of olfactory receptor cells

Glomeruli

Nelken Duft

Oktanol

Odors are coded at the level of the antennal lobe (and the olfactory bulb) in a combinatorial patternof overlapping glomerular activities.

Aliphatic alcohols of different carbon chain length

1-Octanolrepetativestimulation

QuickTime™ and a decompressor

are needed to see this picture.

Odor stimulation leads to bothexcitatory and inhibitory activityIn different glomeruli

Antennal lobe of the beeOdor induced Ca signals

Antagonistic components shape odor coding

What do these effects implicate for the AL-network?

Ringer

PTX

?

GABA

His

(GABA-IR)

homomericLI

Silke Sachse, Giovanni Galicia

-0.10

-0.12

0.70

0.53

0.31

0.93

Odor specific patterns correlate less inPN measurements

Glomeruli

von anderen

zu anderenGlomeruli

inhibitorischeNeurone

Projektionsneurone

Rezeptoraxone

aus Squire et al. Abb. 24.19

Die inhibitorische Verschaltung imolfakt. Bulbus/Antennallobus gleichtder in der Retina: es gibt zwei Ebenen derinhibitorischen lateralen Verschaltung

Retina

Olfaktor. Bulbus

lip: olfactory

collar:visual

basalring:mixed

The calyces of the mb are organized according to sensory modalities

Kirschner et al. 06 Wulfila Gronenburg

olfactory inputvisual input

gustatory input

Schroeter and Menzel 03

Ca2+ Imaging PNs and Kenyon cells

PN glomeruli

PN boutons

KC dendrites

KC somata

PN

KC

Antennallobe

Mushroom body

sites of dye injection(Fura 2 dextran)

selective staining ofPNs and KCs

min F/F max

raw fluorescnece images odor induced KC signal

Odors evoke patterns of activity increase and decreaseat the input to the mushroom body

Nobu Yamagada, unpubl. 07

Odor specific combinatorial codes at three levels

1-hexanol limonen linalool 2-octanolmax

min

F/F

averages of 3 stimulations

lio

lioKenyon cells

PN boutons

PN dendrites

Paul Szyszka et al. 2005

odor

3 s

PN boutons

P. Szyska et al. 2005 .F/F

+

1-hexanol

Kenyon cells respond only transiently to odors(sparse time code)

mean KC and PN responses

clawed Kenyon cell

projectionneuron

Sparsening of the combinatorial population codes at three levels of olfactory integration

max

min

1-hexanol

lio

lioKenyon cells

PN boutons

PN dendrites

neuropil

neuropilsomata

P. Szyska et al. 2005

A small proportion of the clawedKenyon cells respond (1%).

Boutons of projection neuronsshow excitatory and inhibitoryresponses.

The postsynaptic sides of glomeruli(projection neurons) show excitatory and inhibitory responses. A large proportion respond: 25%

F/F

+

-

inhN

PN

KN

KN

KN

DG

microglomerulus

PN

Organizationof the micro-glomerulus

Dirk Müller

Olga Ganeshinamodulatory input,VUMmx1

Jürgen Rybak

PN

delayedinhibition

release frominhibition

odor

Model of odor processing in the MB lip

• transformation of the complex temporal PN response into a binary Kenyon cell response

integrationwhithin 200 ms

localinhibition

KCPN exc.PN inh.

KC

-- ---

- -+

++ + +

+

+Antennallobe

Mushroom body

Paul Szyska et al. 2005

microcircuit of the lip

Ganeshina, MenzelJ. comp. Neurol. 2001

-

Registration of 2 projection neurons und 1 local interneurons in the standard atlas of the bee brain

Morphological networks: Olfactory interneurons

Projection neurons

recordingsite

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

First 3 PCs: 83% variance.

CS+

CS-

Ctr

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-strapProcedure)