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Olfactory instruction for fear: neural system analysis.

Canteras NS, Pavesi E, Carobrez AP - Front Neurosci (2015)

Bottom Line: Studies using cat odor have led to detailed mapping of the neural sites involved in innate and contextual fear responses.Here, we reviewed three lines of work examining the dynamics of the neural systems that organize innate and learned fear responses to cat odor.In the first section, we explored the neural systems involved in innate fear responses and in the acquisition and expression of fear conditioning to cat odor, with a particular emphasis on the role of the dorsal premammillary nucleus (PMd) and the dorsolateral periaqueductal gray (PAGdl), which are key sites that influence innate fear and contextual conditioning.

View Article: PubMed Central - PubMed

Affiliation: Department of Anatomy, Institute of Biomedical Sciences, University of São Paulo São Paulo, Brazil.

ABSTRACT
Different types of predator odors engage elements of the hypothalamic predator-responsive circuit, which has been largely investigated in studies using cat odor exposure. Studies using cat odor have led to detailed mapping of the neural sites involved in innate and contextual fear responses. Here, we reviewed three lines of work examining the dynamics of the neural systems that organize innate and learned fear responses to cat odor. In the first section, we explored the neural systems involved in innate fear responses and in the acquisition and expression of fear conditioning to cat odor, with a particular emphasis on the role of the dorsal premammillary nucleus (PMd) and the dorsolateral periaqueductal gray (PAGdl), which are key sites that influence innate fear and contextual conditioning. In the second section, we reviewed how chemical stimulation of the PMd and PAGdl may serve as a useful unconditioned stimulus in an olfactory fear conditioning paradigm; these experiments provide an interesting perspective for the understanding of learned fear to predator odor. Finally, in the third section, we explored the fact that neutral odors that acquire an aversive valence in a shock-paired conditioning paradigm may mimic predator odor and mobilize elements of the hypothalamic predator-responsive circuit.

No MeSH data available.


Related in: MedlinePlus

Effects of dorsal premammillary nucleus (PMd) application of the beta-adrenoceptor antagonist atenolol (ATE; 10–40 nmol; 0.3 μl on the defensive behavior of rats exposed to an olfactory conditioned stimulus (CS). The familiarization session and the olfactory (CS1) and context (CS2) sessions (10 min in duration) were conducted over three consecutive days. The parameters analyzed were plotted as the mean (+SEM) and were represented in histograms as the percentage of time spent approaching the odor source (top panel), hiding in the enclosed compartment (middle) and stretching out from the enclosed compartment toward the open compartment (head-out; bottom) during the CS1 or CS2 test session. The hatched horizontal bars represent the confidence limit intervals (within 95%) obtained during the familiarization session. The subjects (n = 8–12) received PBS (n = 9) or 10 (n = 8) or 40 (n = 8) nmol ATE, which was administered into the PMd 10 min before the rats were exposed to the CS1 (amyl acetate 5%). ATE OUT (n = 12) represents rats in which the cannula was placed outside the PMd. *p < 0.05, compared with the PBS control group (repeated measures ANOVA followed by Newman–Keuls' post-hoc test).
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Figure 5: Effects of dorsal premammillary nucleus (PMd) application of the beta-adrenoceptor antagonist atenolol (ATE; 10–40 nmol; 0.3 μl on the defensive behavior of rats exposed to an olfactory conditioned stimulus (CS). The familiarization session and the olfactory (CS1) and context (CS2) sessions (10 min in duration) were conducted over three consecutive days. The parameters analyzed were plotted as the mean (+SEM) and were represented in histograms as the percentage of time spent approaching the odor source (top panel), hiding in the enclosed compartment (middle) and stretching out from the enclosed compartment toward the open compartment (head-out; bottom) during the CS1 or CS2 test session. The hatched horizontal bars represent the confidence limit intervals (within 95%) obtained during the familiarization session. The subjects (n = 8–12) received PBS (n = 9) or 10 (n = 8) or 40 (n = 8) nmol ATE, which was administered into the PMd 10 min before the rats were exposed to the CS1 (amyl acetate 5%). ATE OUT (n = 12) represents rats in which the cannula was placed outside the PMd. *p < 0.05, compared with the PBS control group (repeated measures ANOVA followed by Newman–Keuls' post-hoc test).

Mentions: We have further tested the role of beta-adrenergic transmission in the PMd to investigate its participation in the expression of shock-based olfactory fear conditioning. Animals were subjected to the shock-based olfactory fear conditioning protocol as previously described. On day 4, prior to the expression of olfactory fear conditioning, the rats were divided into four groups: the control group (PBS), atenolol outside the PMd (ATE-out), and atenolol in the PMD (10 nmol of ATE-10 or 40 nmol of ATE-40). The rats were microinjected into the PMd, and 10 min later, were placed in the apparatus in the presence of the CS-neutral odor. As shown in Figure 5, in contrast to the animals of the other experimental groups (the PBS and the ATE-out groups), the animals in which atenolol was injected into the PMd (the ATE-10 and ATE-40 groups) showed a significant increase in approach time and a significant decrease in hiding and head-out times during exposure to the footshock-paired odor (CS-neutral odor) as well as decreased contextual defensive responses on the following day, as demonstrated by a significant increase in the time the animals spent approaching a neutral cloth and a decreased hide time. Taken together, the experimental data suggest that the PMd may influence both the expression of olfactory fear conditioning and CS1-CS2 second-order contextual conditioning.


Olfactory instruction for fear: neural system analysis.

Canteras NS, Pavesi E, Carobrez AP - Front Neurosci (2015)

Effects of dorsal premammillary nucleus (PMd) application of the beta-adrenoceptor antagonist atenolol (ATE; 10–40 nmol; 0.3 μl on the defensive behavior of rats exposed to an olfactory conditioned stimulus (CS). The familiarization session and the olfactory (CS1) and context (CS2) sessions (10 min in duration) were conducted over three consecutive days. The parameters analyzed were plotted as the mean (+SEM) and were represented in histograms as the percentage of time spent approaching the odor source (top panel), hiding in the enclosed compartment (middle) and stretching out from the enclosed compartment toward the open compartment (head-out; bottom) during the CS1 or CS2 test session. The hatched horizontal bars represent the confidence limit intervals (within 95%) obtained during the familiarization session. The subjects (n = 8–12) received PBS (n = 9) or 10 (n = 8) or 40 (n = 8) nmol ATE, which was administered into the PMd 10 min before the rats were exposed to the CS1 (amyl acetate 5%). ATE OUT (n = 12) represents rats in which the cannula was placed outside the PMd. *p < 0.05, compared with the PBS control group (repeated measures ANOVA followed by Newman–Keuls' post-hoc test).
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Figure 5: Effects of dorsal premammillary nucleus (PMd) application of the beta-adrenoceptor antagonist atenolol (ATE; 10–40 nmol; 0.3 μl on the defensive behavior of rats exposed to an olfactory conditioned stimulus (CS). The familiarization session and the olfactory (CS1) and context (CS2) sessions (10 min in duration) were conducted over three consecutive days. The parameters analyzed were plotted as the mean (+SEM) and were represented in histograms as the percentage of time spent approaching the odor source (top panel), hiding in the enclosed compartment (middle) and stretching out from the enclosed compartment toward the open compartment (head-out; bottom) during the CS1 or CS2 test session. The hatched horizontal bars represent the confidence limit intervals (within 95%) obtained during the familiarization session. The subjects (n = 8–12) received PBS (n = 9) or 10 (n = 8) or 40 (n = 8) nmol ATE, which was administered into the PMd 10 min before the rats were exposed to the CS1 (amyl acetate 5%). ATE OUT (n = 12) represents rats in which the cannula was placed outside the PMd. *p < 0.05, compared with the PBS control group (repeated measures ANOVA followed by Newman–Keuls' post-hoc test).
Mentions: We have further tested the role of beta-adrenergic transmission in the PMd to investigate its participation in the expression of shock-based olfactory fear conditioning. Animals were subjected to the shock-based olfactory fear conditioning protocol as previously described. On day 4, prior to the expression of olfactory fear conditioning, the rats were divided into four groups: the control group (PBS), atenolol outside the PMd (ATE-out), and atenolol in the PMD (10 nmol of ATE-10 or 40 nmol of ATE-40). The rats were microinjected into the PMd, and 10 min later, were placed in the apparatus in the presence of the CS-neutral odor. As shown in Figure 5, in contrast to the animals of the other experimental groups (the PBS and the ATE-out groups), the animals in which atenolol was injected into the PMd (the ATE-10 and ATE-40 groups) showed a significant increase in approach time and a significant decrease in hiding and head-out times during exposure to the footshock-paired odor (CS-neutral odor) as well as decreased contextual defensive responses on the following day, as demonstrated by a significant increase in the time the animals spent approaching a neutral cloth and a decreased hide time. Taken together, the experimental data suggest that the PMd may influence both the expression of olfactory fear conditioning and CS1-CS2 second-order contextual conditioning.

Bottom Line: Studies using cat odor have led to detailed mapping of the neural sites involved in innate and contextual fear responses.Here, we reviewed three lines of work examining the dynamics of the neural systems that organize innate and learned fear responses to cat odor.In the first section, we explored the neural systems involved in innate fear responses and in the acquisition and expression of fear conditioning to cat odor, with a particular emphasis on the role of the dorsal premammillary nucleus (PMd) and the dorsolateral periaqueductal gray (PAGdl), which are key sites that influence innate fear and contextual conditioning.

View Article: PubMed Central - PubMed

Affiliation: Department of Anatomy, Institute of Biomedical Sciences, University of São Paulo São Paulo, Brazil.

ABSTRACT
Different types of predator odors engage elements of the hypothalamic predator-responsive circuit, which has been largely investigated in studies using cat odor exposure. Studies using cat odor have led to detailed mapping of the neural sites involved in innate and contextual fear responses. Here, we reviewed three lines of work examining the dynamics of the neural systems that organize innate and learned fear responses to cat odor. In the first section, we explored the neural systems involved in innate fear responses and in the acquisition and expression of fear conditioning to cat odor, with a particular emphasis on the role of the dorsal premammillary nucleus (PMd) and the dorsolateral periaqueductal gray (PAGdl), which are key sites that influence innate fear and contextual conditioning. In the second section, we reviewed how chemical stimulation of the PMd and PAGdl may serve as a useful unconditioned stimulus in an olfactory fear conditioning paradigm; these experiments provide an interesting perspective for the understanding of learned fear to predator odor. Finally, in the third section, we explored the fact that neutral odors that acquire an aversive valence in a shock-paired conditioning paradigm may mimic predator odor and mobilize elements of the hypothalamic predator-responsive circuit.

No MeSH data available.


Related in: MedlinePlus