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The participation of cortical amygdala in innate, odour-driven behaviour.

Root CM, Denny CA, Hen R, Axel R - Nature (2014)

Bottom Line: Moreover, we use the promoter of the activity-dependent gene arc to express the photosensitive ion channel, channelrhodopsin, in neurons of the cortical amygdala activated by odours that elicit innate behaviours.Optical activation of these neurons leads to appropriate behaviours that recapitulate the responses to innate odours.These data indicate that the cortical amygdala plays a critical role in generating innate odour-driven behaviours but do not preclude its participation in learned olfactory behaviours.

View Article: PubMed Central - PubMed

Affiliation: Department of Neuroscience and the Howard Hughes Medical Institute, College of Physicians and Surgeons, Columbia University, New York, New York 10032, USA.

ABSTRACT
Innate behaviours are observed in naive animals without prior learning or experience, suggesting that the neural circuits that mediate these behaviours are genetically determined and stereotyped. The neural circuits that convey olfactory information from the sense organ to the cortical and subcortical olfactory centres have been anatomically defined, but the specific pathways responsible for innate responses to volatile odours have not been identified. Here we devise genetic strategies that demonstrate that a stereotyped neural circuit that transmits information from the olfactory bulb to cortical amygdala is necessary for innate aversive and appetitive behaviours. Moreover, we use the promoter of the activity-dependent gene arc to express the photosensitive ion channel, channelrhodopsin, in neurons of the cortical amygdala activated by odours that elicit innate behaviours. Optical activation of these neurons leads to appropriate behaviours that recapitulate the responses to innate odours. These data indicate that the cortical amygdala plays a critical role in generating innate odour-driven behaviours but do not preclude its participation in learned olfactory behaviours.

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Activation of odor responsive neurons within cortical amygdala is sufficient to recapitulate behavioral responsesa, The genetic strategy used to express ChR2 in odor responsive neurons. The tamoxifen sensitive Cre recombinase, CreERT2, was expressed under the control of the promoter of the activity-dependent gene, arc, in a transgenic mouse. The gene encoding Cre-dependent ChR2-eYFP was introduced into the cortical amygdala by infection with AAV5. b, The timeline for experimental manipulations. The animal was sampled upon termination of behavioral testing. c, Representative images showing the expression of ChR2-eYFP in mice that received tamoxifen injection followed by exposure to either the odorant isoamyl acetate (bottom) or no odor as a control (top). Scale bar indicates 300 μm. d-f, Mice with odor-driven channelrhodopsin expression were tested in the open field assay where they received pulsed photoactivation upon entrance into one quadrant. The percent time each animal spent in the lower right quadrant in the absence and presence of pulsed photoactivation in mice with neurons activated by TMT (d), 2-phenylethanol (e) and isoamyl acetate (f). g, The average performance index for mice receiving photostimulation of neurons activated by TMT, 2-phenylethanol, isoamyl acetate, or no odor, respectively from left to right (n=3-6). **P < 0.01, ***P < 0.001 t-test comparing PI with and without laser; error bars indicate SEM.
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Figure 3: Activation of odor responsive neurons within cortical amygdala is sufficient to recapitulate behavioral responsesa, The genetic strategy used to express ChR2 in odor responsive neurons. The tamoxifen sensitive Cre recombinase, CreERT2, was expressed under the control of the promoter of the activity-dependent gene, arc, in a transgenic mouse. The gene encoding Cre-dependent ChR2-eYFP was introduced into the cortical amygdala by infection with AAV5. b, The timeline for experimental manipulations. The animal was sampled upon termination of behavioral testing. c, Representative images showing the expression of ChR2-eYFP in mice that received tamoxifen injection followed by exposure to either the odorant isoamyl acetate (bottom) or no odor as a control (top). Scale bar indicates 300 μm. d-f, Mice with odor-driven channelrhodopsin expression were tested in the open field assay where they received pulsed photoactivation upon entrance into one quadrant. The percent time each animal spent in the lower right quadrant in the absence and presence of pulsed photoactivation in mice with neurons activated by TMT (d), 2-phenylethanol (e) and isoamyl acetate (f). g, The average performance index for mice receiving photostimulation of neurons activated by TMT, 2-phenylethanol, isoamyl acetate, or no odor, respectively from left to right (n=3-6). **P < 0.01, ***P < 0.001 t-test comparing PI with and without laser; error bars indicate SEM.

Mentions: Our data suggest that distinct cell populations that reside within the cortical amygdala are capable of eliciting innate responses to either appetitive or aversive odors. We next identified and manipulated the activity of these neurons by exploiting the promoter of the activity-dependent gene, arc19, to drive the expression of the light activated cation channel, channelrhodopsin20. AAV encoding a Cre-dependent channelrhodopsin fused to the fluorescent protein eYFP (AAV-ef1α-DIO-ChR2-eYFP) was injected into the cortical amygdala of mice harboring a transgene in which the arc promoter drives the expression of the tamoxifen-sensitive Cre-recombinase (CreERT2) (Fig. 3a). In this ArcCreERT2 mouse21, neuronal activation should result in the expression of CreERT2. In the presence of tamoxifen, activated Cre will effect the recombination between the loxP sites of AAV-ef1α-DIO-ChR2, resulting in the irreversible expression of ChR2-eYFP. The fusion of Cre with the tamoxifen-sensitive estrogen receptor allows for temporal control of the recombination activity. Thus administration of tamoxifen followed by exposure to odor should result in the expression of ChR2-eYFP in the neurons activated by the odor (Fig. 3b,c), permitting us to mark and manipulate the activity of these neural populations.


The participation of cortical amygdala in innate, odour-driven behaviour.

Root CM, Denny CA, Hen R, Axel R - Nature (2014)

Activation of odor responsive neurons within cortical amygdala is sufficient to recapitulate behavioral responsesa, The genetic strategy used to express ChR2 in odor responsive neurons. The tamoxifen sensitive Cre recombinase, CreERT2, was expressed under the control of the promoter of the activity-dependent gene, arc, in a transgenic mouse. The gene encoding Cre-dependent ChR2-eYFP was introduced into the cortical amygdala by infection with AAV5. b, The timeline for experimental manipulations. The animal was sampled upon termination of behavioral testing. c, Representative images showing the expression of ChR2-eYFP in mice that received tamoxifen injection followed by exposure to either the odorant isoamyl acetate (bottom) or no odor as a control (top). Scale bar indicates 300 μm. d-f, Mice with odor-driven channelrhodopsin expression were tested in the open field assay where they received pulsed photoactivation upon entrance into one quadrant. The percent time each animal spent in the lower right quadrant in the absence and presence of pulsed photoactivation in mice with neurons activated by TMT (d), 2-phenylethanol (e) and isoamyl acetate (f). g, The average performance index for mice receiving photostimulation of neurons activated by TMT, 2-phenylethanol, isoamyl acetate, or no odor, respectively from left to right (n=3-6). **P < 0.01, ***P < 0.001 t-test comparing PI with and without laser; error bars indicate SEM.
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Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4231015&req=5

Figure 3: Activation of odor responsive neurons within cortical amygdala is sufficient to recapitulate behavioral responsesa, The genetic strategy used to express ChR2 in odor responsive neurons. The tamoxifen sensitive Cre recombinase, CreERT2, was expressed under the control of the promoter of the activity-dependent gene, arc, in a transgenic mouse. The gene encoding Cre-dependent ChR2-eYFP was introduced into the cortical amygdala by infection with AAV5. b, The timeline for experimental manipulations. The animal was sampled upon termination of behavioral testing. c, Representative images showing the expression of ChR2-eYFP in mice that received tamoxifen injection followed by exposure to either the odorant isoamyl acetate (bottom) or no odor as a control (top). Scale bar indicates 300 μm. d-f, Mice with odor-driven channelrhodopsin expression were tested in the open field assay where they received pulsed photoactivation upon entrance into one quadrant. The percent time each animal spent in the lower right quadrant in the absence and presence of pulsed photoactivation in mice with neurons activated by TMT (d), 2-phenylethanol (e) and isoamyl acetate (f). g, The average performance index for mice receiving photostimulation of neurons activated by TMT, 2-phenylethanol, isoamyl acetate, or no odor, respectively from left to right (n=3-6). **P < 0.01, ***P < 0.001 t-test comparing PI with and without laser; error bars indicate SEM.
Mentions: Our data suggest that distinct cell populations that reside within the cortical amygdala are capable of eliciting innate responses to either appetitive or aversive odors. We next identified and manipulated the activity of these neurons by exploiting the promoter of the activity-dependent gene, arc19, to drive the expression of the light activated cation channel, channelrhodopsin20. AAV encoding a Cre-dependent channelrhodopsin fused to the fluorescent protein eYFP (AAV-ef1α-DIO-ChR2-eYFP) was injected into the cortical amygdala of mice harboring a transgene in which the arc promoter drives the expression of the tamoxifen-sensitive Cre-recombinase (CreERT2) (Fig. 3a). In this ArcCreERT2 mouse21, neuronal activation should result in the expression of CreERT2. In the presence of tamoxifen, activated Cre will effect the recombination between the loxP sites of AAV-ef1α-DIO-ChR2, resulting in the irreversible expression of ChR2-eYFP. The fusion of Cre with the tamoxifen-sensitive estrogen receptor allows for temporal control of the recombination activity. Thus administration of tamoxifen followed by exposure to odor should result in the expression of ChR2-eYFP in the neurons activated by the odor (Fig. 3b,c), permitting us to mark and manipulate the activity of these neural populations.

Bottom Line: Moreover, we use the promoter of the activity-dependent gene arc to express the photosensitive ion channel, channelrhodopsin, in neurons of the cortical amygdala activated by odours that elicit innate behaviours.Optical activation of these neurons leads to appropriate behaviours that recapitulate the responses to innate odours.These data indicate that the cortical amygdala plays a critical role in generating innate odour-driven behaviours but do not preclude its participation in learned olfactory behaviours.

View Article: PubMed Central - PubMed

Affiliation: Department of Neuroscience and the Howard Hughes Medical Institute, College of Physicians and Surgeons, Columbia University, New York, New York 10032, USA.

ABSTRACT
Innate behaviours are observed in naive animals without prior learning or experience, suggesting that the neural circuits that mediate these behaviours are genetically determined and stereotyped. The neural circuits that convey olfactory information from the sense organ to the cortical and subcortical olfactory centres have been anatomically defined, but the specific pathways responsible for innate responses to volatile odours have not been identified. Here we devise genetic strategies that demonstrate that a stereotyped neural circuit that transmits information from the olfactory bulb to cortical amygdala is necessary for innate aversive and appetitive behaviours. Moreover, we use the promoter of the activity-dependent gene arc to express the photosensitive ion channel, channelrhodopsin, in neurons of the cortical amygdala activated by odours that elicit innate behaviours. Optical activation of these neurons leads to appropriate behaviours that recapitulate the responses to innate odours. These data indicate that the cortical amygdala plays a critical role in generating innate odour-driven behaviours but do not preclude its participation in learned olfactory behaviours.

Show MeSH
Related in: MedlinePlus