Download Smell Prism - Systems Neuroscience Course, MEDS 371, Univ

University of Connecticut Graduate School
MEDS 371: Systems Neuroscience
2011
Chemosensory Systems
Marion E. Frank, Ph.D.
Professor
Center for Chemosensory Sciences
Oral Health & Diagnostic Sciences
School of Dental Medicine
OLFACTORY SYSTEM
Purpose of Smell---Detect, Analyze Valuable or Dangerous
Environmental Chemicals
Chemicals that Smell: Vapors, Names
camphoraceous: hexachloroethane
floral: 2-amyl pyridine
pepperminty: l-menthol
ethereal: diethyl ether
Putrid
pungent: formic acid
putrid: hydrogen sulfide
musky: xylene musk
Peripheral
Labeled Lines
Odor Receptors
and Mitral Cells in
Olfactory Bulb
Red = ?
Green = ?
Blue = ?
From Axel and Buck, 2005
1000 GPCR odor receptors (OR)
From Buck, 2005
Odor Transduction
Adaptation, PKA
Rapid Adaptation
Species Differences in Olfaction
Main Olfactory System -- Vomeronasal System
MOE = main olfactory epithelium
MOB = main olfactory bulb
AON = anterior olfactory nucleus
PC = piriform cortex
OT = olfactory tubercle
LA = lateral amygdala
EC = entorhinal cortex
VNO = vomeronasal organ
AOB = accessory olfactory bulb
MeA = medial amygdala
Dulac & Wagner, 2006
Rodent Olfactory Bulb
OSNs
Rapid Adaptation
Mixture Suppression
Glom = glomerulus, OSN = olfactory
sensory neuron
Inhibitory Neurons: PG = periglomerular
cell, G = granule cell,
Output Neurons: M = mitral cell
lateral
olfactory tract
Schoppa and Urban, 2003
Olfactory Epithelium Cells, Turnover,
Target in Olfactory Bulb
Olfactory Sensory Neuron Generation in Adults
Sus = Sustentacular (supporting) cell, HBC = Horizontal Basal Cell
GBC = Globose Basal Cell; mpp multipotent progenitor, ta = transit amplifying,
inp = immediate neuronal precursor.
OSN = Olfactory Sensory Neuron; i = immature, m = mature.
Schwob, 2002.
Human Nasal Cavity, Sniffing
Ortho- vs. Retronasal
MOE: Recordings, Apical and Basal
Functional Units in Olfactory Bulb
Morphological substrates
for inhibition.
ON = olfactory nerve
PG = periglomerular cell
M = mitral cell
GR = granule cell
AON = anterior olfactory
nucleus
Morphological substrates for specific input-output functions.
Responses of Olfactory Bulb Neurons
 = stimulus delivery
N = no response
S1, S2 = suppression
E1, E2, E3 = excitation
At top, phases of electro-olfactogram (EOG) are represented by
Roman numerals (I, II, III, IV) (Kauer, 1974).
Central Olfactory Pathways: Rodent
Rodents: Macrosmic
>1000 OR
AON: anterior olfactory nucleus, PC: piriform cortex, OT: olfactory tubercle,
AM: anterior cortical amygdaloid nucleus, TER: lateral entorhinal cortex
ODOR CODING
Odor stimuli to test with Monoclonal Nose in Mice.
O
pungent,
orange
pine tar,
turpentine
(+)/(–)
Alpha-Pinene
Acetophenone
O
rose-like
lily
OH
(+)/(–) Beta-Citronellol
O
Ethyl Acetate
nail polish,
fruity
Mice with a “Monclonal Nose”… Fleischmann et al. 2008
●= control ▲ = transgenic, 95% ORN express M71 (ligand Acetophenone)
Go/No-go Fraction Correct
Ethyl Acetate, –/+ Citronellol
Block of Trials
Mice with a “Monclonal Nose”… Fleischmann et al. 2008
●= control ▲ = transgenic, 95% ORN express M71 (ligand Acetophenone)
Go/No-go Fraction Correct
Ethyl Acetate, –/+ Pinene
Block of Trials
Mice with a “Monclonal Nose”… Fleischmann et al. 2008
●= control ▲ = transgenic, 95% ORN express M71 (ligand Acetophenone)
Go/No-go Fraction Correct
Acetophenone, Air
Block of Trials
Mice with a “Monclonal Nose”… Fleischmann et al. 2008
●= control ▲ = transgenic, 95% ORN express M71 (ligand Acetophenone)
Go/No-go Fraction Correct
Acetophenone = Air
Air
Air
Air
Air
Block of Trials
See B
NATURAL SCENTS
100s of Chemical
Components in Scent
Representation in Few
Glomeruli in Rodents
Few Dominant Cues
Inhibitory Interactions
among Glomeruli
Dulac, 2006
Central Olfactory Pathways: Human
Humans:Microsmic
~300 OR
Odor Mixtures: Humans
Single
Compound
Vanillin
Mixture
Component
Single
Compound
PEA
•V = 5 mM vanillin, v = 1 mM
vanillin
•R = 5 mM PEA, r = 1 mM PEA.
• 0 = water
•Gold background highlights
correct responses of 10 subjects in
each session
• The 31 adapt-test pairs were
presented to each subject in each
session
•Average % correct Identification
for the 2 sessions is listed at right
•PEA = phenethyl alcohol odor
Rose
ODOR CODING:
Rapid Adaptation & Mixture Suppression
Single Compounds
Controls
From Frank et al, 2010
Mixture Components
Controls
Convergence of Taste and Smell in Orbitofrontal Cortex
From Rolls, 2004
Olfactory System Summary









Smell is a chemical sense that evaluates vaporous environmental chemicals.
We perceive many odor qualities, notes perhaps each associated with one of the
hundreds of olfactory receptors (OR).
Olfactory sensory neurons (OSN) have dendrites with cilia containing a G-protiencoupled OR and axons that communicate to the olfactory bulb.
OSN can regenerate, giving them an unusual ability to recover from injury.
OSN located in separate regions use 4 subfamilies of OR, individual OSN express
single OR variants, and all OSN expressing one of the hundreds of variants project
to a few glomeruli in the olfactory bulb.
OSN may respond to many compounds, generating distinct spatial-temporal
patterns of neural activity for each odor.
Olfactory bulb output neurons, mitral and tufted cells, relay olfactory signals to
higher levels, and periglomerular and granule inhibitory neurons, which are
generated throughout adult life, modify olfactory signals within the bulb.
Olfactory signals are relayed from the olfactory bulb to the olfactory paleo-cortex,
then thalamus and cerebral cortex, where odor qualities are discriminated.
Projections to the hypothalamus and hippocampus are sites where experience and
emotion interact with odor.
The End