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Dissecting the role of TRPV1 in detecting multiple trigeminal irritants in three behavioral assays for sensory irritation.

Saunders CJ, Li WY, Patel TD, Muday JA, Silver WL - F1000Res (2013)

Bottom Line: However, the mechanism of stimulation is known only for relatively few of these compounds.Capsaicin, for example, activates transient receptor potential vanilloid 1 (TRPV1) channels.However, cyclohexanone was the only substance tested that appears to act solely through TRPV1.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, Wake Forest University, Winston-Salem, NC, 27109, USA ; Rocky Mountain Taste and Smell Center, Neuroscience Program, Department of Cell and Developmental Biology, University of Colorado, Anschutz Medical Campus, Aurora, CO, 80045, USA.

ABSTRACT
Polymodal neurons of the trigeminal nerve innervate the nasal cavity, nasopharynx, oral cavity and cornea. Trigeminal nociceptive fibers express a diverse collection of receptors and are stimulated by a wide variety of chemicals. However, the mechanism of stimulation is known only for relatively few of these compounds. Capsaicin, for example, activates transient receptor potential vanilloid 1 (TRPV1) channels. In the present study, wildtype (C57Bl/6J) and TRPV1 knockout mice were tested in three behavioral assays for irritation to determine if TRPV1 is necessary to detect trigeminal irritants in addition to capsaicin. In one assay mice were presented with a chemical via a cotton swab and their response scored on a 5 level scale. In another assay, a modified two bottle preference test, which avoids the confound of mixing irritants with the animal's drinking water, was used to assess aversion. In the final assay, an air dilution olfactometer was used to administer volatile compounds to mice restrained in a double-chambered plethysmograph where respiratory reflexes were monitored. TRPV1 knockouts showed deficiencies in the detection of benzaldehyde, cyclohexanone and eugenol in at least one assay. However, cyclohexanone was the only substance tested that appears to act solely through TRPV1.

No MeSH data available.


Related in: MedlinePlus

TRPV1 knockout mice are significantly less averse to capsaicin and cyclohexanone than wildtype mice in an acute presentation.(A) A five-point scale ranging from -2 for a trigeminal reflex to +2 for a highly favorable response was used to assign behavioral scores for each substance. (B) Mean ± SEM behavioral score for wildtype mice (n=7), filled bars, and TRPV1-/- knockout mice (n=7), unfilled bars. Two-way ANOVA revealed a significant difference among irritants (P<0.001), genotype (P<0.01) and a significant interaction between irritant and genotype (P<0.05). Knockout mice had a significantly more favorable response to capsaicin (P<0.01) and cyclohexanone (P<0.05) than wildtype mice. *P<0.05, **P<0.01, ***P<0.001.
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f2: TRPV1 knockout mice are significantly less averse to capsaicin and cyclohexanone than wildtype mice in an acute presentation.(A) A five-point scale ranging from -2 for a trigeminal reflex to +2 for a highly favorable response was used to assign behavioral scores for each substance. (B) Mean ± SEM behavioral score for wildtype mice (n=7), filled bars, and TRPV1-/- knockout mice (n=7), unfilled bars. Two-way ANOVA revealed a significant difference among irritants (P<0.001), genotype (P<0.01) and a significant interaction between irritant and genotype (P<0.05). Knockout mice had a significantly more favorable response to capsaicin (P<0.01) and cyclohexanone (P<0.05) than wildtype mice. *P<0.05, **P<0.01, ***P<0.001.

Mentions: Cotton swabs saturated with an irritant were presented to wildtype (n=7) and TRPV1 (n=7) knockout mice to determine whether TRPV1 is necessary for detection of an acute presentation of an irritating compound. The response to these compounds was scored on a five-point scale. The scale ranged from -2 for a reflexive trigeminal response, to 0 for no response to the cotton swab, to +2 for feeding behavior (summarized inFigure 2A). Two-factor ANOVA revealed a significant difference between irritants (P<0.001), genotype (P<0.01) and a significant interaction between irritant and genotype (P<0.05).


Dissecting the role of TRPV1 in detecting multiple trigeminal irritants in three behavioral assays for sensory irritation.

Saunders CJ, Li WY, Patel TD, Muday JA, Silver WL - F1000Res (2013)

TRPV1 knockout mice are significantly less averse to capsaicin and cyclohexanone than wildtype mice in an acute presentation.(A) A five-point scale ranging from -2 for a trigeminal reflex to +2 for a highly favorable response was used to assign behavioral scores for each substance. (B) Mean ± SEM behavioral score for wildtype mice (n=7), filled bars, and TRPV1-/- knockout mice (n=7), unfilled bars. Two-way ANOVA revealed a significant difference among irritants (P<0.001), genotype (P<0.01) and a significant interaction between irritant and genotype (P<0.05). Knockout mice had a significantly more favorable response to capsaicin (P<0.01) and cyclohexanone (P<0.05) than wildtype mice. *P<0.05, **P<0.01, ***P<0.001.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC3814916&req=5

f2: TRPV1 knockout mice are significantly less averse to capsaicin and cyclohexanone than wildtype mice in an acute presentation.(A) A five-point scale ranging from -2 for a trigeminal reflex to +2 for a highly favorable response was used to assign behavioral scores for each substance. (B) Mean ± SEM behavioral score for wildtype mice (n=7), filled bars, and TRPV1-/- knockout mice (n=7), unfilled bars. Two-way ANOVA revealed a significant difference among irritants (P<0.001), genotype (P<0.01) and a significant interaction between irritant and genotype (P<0.05). Knockout mice had a significantly more favorable response to capsaicin (P<0.01) and cyclohexanone (P<0.05) than wildtype mice. *P<0.05, **P<0.01, ***P<0.001.
Mentions: Cotton swabs saturated with an irritant were presented to wildtype (n=7) and TRPV1 (n=7) knockout mice to determine whether TRPV1 is necessary for detection of an acute presentation of an irritating compound. The response to these compounds was scored on a five-point scale. The scale ranged from -2 for a reflexive trigeminal response, to 0 for no response to the cotton swab, to +2 for feeding behavior (summarized inFigure 2A). Two-factor ANOVA revealed a significant difference between irritants (P<0.001), genotype (P<0.01) and a significant interaction between irritant and genotype (P<0.05).

Bottom Line: However, the mechanism of stimulation is known only for relatively few of these compounds.Capsaicin, for example, activates transient receptor potential vanilloid 1 (TRPV1) channels.However, cyclohexanone was the only substance tested that appears to act solely through TRPV1.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, Wake Forest University, Winston-Salem, NC, 27109, USA ; Rocky Mountain Taste and Smell Center, Neuroscience Program, Department of Cell and Developmental Biology, University of Colorado, Anschutz Medical Campus, Aurora, CO, 80045, USA.

ABSTRACT
Polymodal neurons of the trigeminal nerve innervate the nasal cavity, nasopharynx, oral cavity and cornea. Trigeminal nociceptive fibers express a diverse collection of receptors and are stimulated by a wide variety of chemicals. However, the mechanism of stimulation is known only for relatively few of these compounds. Capsaicin, for example, activates transient receptor potential vanilloid 1 (TRPV1) channels. In the present study, wildtype (C57Bl/6J) and TRPV1 knockout mice were tested in three behavioral assays for irritation to determine if TRPV1 is necessary to detect trigeminal irritants in addition to capsaicin. In one assay mice were presented with a chemical via a cotton swab and their response scored on a 5 level scale. In another assay, a modified two bottle preference test, which avoids the confound of mixing irritants with the animal's drinking water, was used to assess aversion. In the final assay, an air dilution olfactometer was used to administer volatile compounds to mice restrained in a double-chambered plethysmograph where respiratory reflexes were monitored. TRPV1 knockouts showed deficiencies in the detection of benzaldehyde, cyclohexanone and eugenol in at least one assay. However, cyclohexanone was the only substance tested that appears to act solely through TRPV1.

No MeSH data available.


Related in: MedlinePlus