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Dual processing of sulfated steroids in the olfactory system of an anuran amphibian.

Sansone A, Hassenklöver T, Offner T, Fu X, Holy TE, Manzini I - Front Cell Neurosci (2015)

Bottom Line: Chemical communication is widespread in amphibians, but if compared to later diverging tetrapods the available functional data is limited.Furthermore, we found that larval and adult animals excrete multiple sulfated compounds with physical properties consistent with sulfated steroids.Breeding tadpole and frog water including these compounds activated a large subset of sensory neurons that also responded to synthetic steroids, showing that sulfated steroids are likely to convey intraspecific information.

View Article: PubMed Central - PubMed

Affiliation: Institute of Neurophysiology and Cellular Biophysics, University of Göttingen Göttingen, Germany ; Center for Nanoscale Microscopy and Molecular Physiology of the Brain Göttingen, Germany.

ABSTRACT
Chemical communication is widespread in amphibians, but if compared to later diverging tetrapods the available functional data is limited. The existing information on the vomeronasal system of anurans is particularly sparse. Amphibians represent a transitional stage in the evolution of the olfactory system. Most species have anatomically separated main and vomeronasal systems, but recent studies have shown that in anurans their molecular separation is still underway. Sulfated steroids function as migratory pheromones in lamprey and have recently been identified as natural vomeronasal stimuli in rodents. Here we identified sulfated steroids as the first known class of vomeronasal stimuli in the amphibian Xenopus laevis. We show that sulfated steroids are detected and concurrently processed by the two distinct olfactory subsystems of larval Xenopus laevis, the main olfactory system and the vomeronasal system. Our data revealed a similar but partially different processing of steroid-induced responses in the two systems. Differences of detection thresholds suggest that the two information channels are not just redundant, but rather signal different information. Furthermore, we found that larval and adult animals excrete multiple sulfated compounds with physical properties consistent with sulfated steroids. Breeding tadpole and frog water including these compounds activated a large subset of sensory neurons that also responded to synthetic steroids, showing that sulfated steroids are likely to convey intraspecific information. Our findings indicate that sulfated steroids are conserved vomeronasal stimuli functioning in phylogenetically distant classes of tetrapods living in aquatic and terrestrial habitats.

No MeSH data available.


Physiological characterization of sulfated steroid responses. (A) Calcium responses of three sensory neurons upon application of sulfated steroid mixtures and of single compounds from each mixture (200 μM). (B) Concentration-dependent response curves for a single component of the P mix (P8168) in sensory neurons of the MOE (9 cells) and the VNO (8 cells). (C) Graphs showing the percentage of responsive neurons having a certain detection threshold. MOE: 0.1–1 μM, 1 cell; 1–10 μM, 8 cells; 10–50 μM, 2 cells (8 slices). VNO: 1–10 μM, 2 cells; 10–50 μM, 10 cells (6 slices). (D) Response profiles of P steroid-sensitive neurons in the MOE (24 cells, 7 slices; response intensities are coded by a color gradient). (E) Response profiles of P steroid-sensitive neurons in the VNO (25 cells, 5 slices). (F) Response profiles of E steroid-sensitive neurons in the MOE (15 cells, 7 slices). (G) Percentage of observed responses to individual sulfated steroids. P steroids showed a similar trend between MOE and VNO, with all three steroids eliciting between 20 and 40% of the total responses. A different trend was detected for E steroids, with one compound of the mixture (E0588) eliciting more than half (~60%) of the observed responses. (H) Venn diagram showing groups of P mix responsive neurons in the MOE. The majority of the neurons (13 cells) responded to all three components of the mixture. (I) Venn diagram showing groups of P mix responsive neurons in the VNO. The two main groups (9 and 8 cells) include neurons responding to two and three chemicals of the P mix. (J) Venn diagram showing groups of E mix responsive neurons in the MOE. The largest group (8 cells) contains neurons responding to only one chemical in the mixture, namely E0588.
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Figure 5: Physiological characterization of sulfated steroid responses. (A) Calcium responses of three sensory neurons upon application of sulfated steroid mixtures and of single compounds from each mixture (200 μM). (B) Concentration-dependent response curves for a single component of the P mix (P8168) in sensory neurons of the MOE (9 cells) and the VNO (8 cells). (C) Graphs showing the percentage of responsive neurons having a certain detection threshold. MOE: 0.1–1 μM, 1 cell; 1–10 μM, 8 cells; 10–50 μM, 2 cells (8 slices). VNO: 1–10 μM, 2 cells; 10–50 μM, 10 cells (6 slices). (D) Response profiles of P steroid-sensitive neurons in the MOE (24 cells, 7 slices; response intensities are coded by a color gradient). (E) Response profiles of P steroid-sensitive neurons in the VNO (25 cells, 5 slices). (F) Response profiles of E steroid-sensitive neurons in the MOE (15 cells, 7 slices). (G) Percentage of observed responses to individual sulfated steroids. P steroids showed a similar trend between MOE and VNO, with all three steroids eliciting between 20 and 40% of the total responses. A different trend was detected for E steroids, with one compound of the mixture (E0588) eliciting more than half (~60%) of the observed responses. (H) Venn diagram showing groups of P mix responsive neurons in the MOE. The majority of the neurons (13 cells) responded to all three components of the mixture. (I) Venn diagram showing groups of P mix responsive neurons in the VNO. The two main groups (9 and 8 cells) include neurons responding to two and three chemicals of the P mix. (J) Venn diagram showing groups of E mix responsive neurons in the MOE. The largest group (8 cells) contains neurons responding to only one chemical in the mixture, namely E0588.

Mentions: We applied the individual components of the P and E mix (see Materials and Methods and Supplementary Table 1) in addition to the mixtures to obtain response profiles of individual neurons of the VNO and the MOE (Figure 5A). Similar responses for the P mix sulfated steroids were obtained in cells of the MOE and the VNO, i.e., in both epithelia most sensory neurons responded to more than one compound of the mixture. This suggests that sensory neurons in both olfactory subsystems are broadly tuned to P mix sulfated steroids (Figures 5D,E). None of the P mix compounds was detected with much higher frequency than the others (Figure 5G). In contrast, the response profiles for E mix steroids in the MOE showed a different trend. One specific compound, i.e., E0588, activated the large majority of cells. The other two compounds were less effective (Figures 5F,G). The Venn diagrams in Figures 5H–J emphasize the above findings. Overall, the average number of P and E mix-sensitive cells in the MOE and the VNO varied considerably (MOE: 5 P mix cells vs. 1.7 E mix cells/slice; VNO: 2.3 P mix cells vs. 0.16 E mix cells/slice; for absolute numbers see Figure 1). E mix-responsive cells in the VNO were too rare (5 cells in 32 slices) to perform a systematic analysis of exact response profiles.


Dual processing of sulfated steroids in the olfactory system of an anuran amphibian.

Sansone A, Hassenklöver T, Offner T, Fu X, Holy TE, Manzini I - Front Cell Neurosci (2015)

Physiological characterization of sulfated steroid responses. (A) Calcium responses of three sensory neurons upon application of sulfated steroid mixtures and of single compounds from each mixture (200 μM). (B) Concentration-dependent response curves for a single component of the P mix (P8168) in sensory neurons of the MOE (9 cells) and the VNO (8 cells). (C) Graphs showing the percentage of responsive neurons having a certain detection threshold. MOE: 0.1–1 μM, 1 cell; 1–10 μM, 8 cells; 10–50 μM, 2 cells (8 slices). VNO: 1–10 μM, 2 cells; 10–50 μM, 10 cells (6 slices). (D) Response profiles of P steroid-sensitive neurons in the MOE (24 cells, 7 slices; response intensities are coded by a color gradient). (E) Response profiles of P steroid-sensitive neurons in the VNO (25 cells, 5 slices). (F) Response profiles of E steroid-sensitive neurons in the MOE (15 cells, 7 slices). (G) Percentage of observed responses to individual sulfated steroids. P steroids showed a similar trend between MOE and VNO, with all three steroids eliciting between 20 and 40% of the total responses. A different trend was detected for E steroids, with one compound of the mixture (E0588) eliciting more than half (~60%) of the observed responses. (H) Venn diagram showing groups of P mix responsive neurons in the MOE. The majority of the neurons (13 cells) responded to all three components of the mixture. (I) Venn diagram showing groups of P mix responsive neurons in the VNO. The two main groups (9 and 8 cells) include neurons responding to two and three chemicals of the P mix. (J) Venn diagram showing groups of E mix responsive neurons in the MOE. The largest group (8 cells) contains neurons responding to only one chemical in the mixture, namely E0588.
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Figure 5: Physiological characterization of sulfated steroid responses. (A) Calcium responses of three sensory neurons upon application of sulfated steroid mixtures and of single compounds from each mixture (200 μM). (B) Concentration-dependent response curves for a single component of the P mix (P8168) in sensory neurons of the MOE (9 cells) and the VNO (8 cells). (C) Graphs showing the percentage of responsive neurons having a certain detection threshold. MOE: 0.1–1 μM, 1 cell; 1–10 μM, 8 cells; 10–50 μM, 2 cells (8 slices). VNO: 1–10 μM, 2 cells; 10–50 μM, 10 cells (6 slices). (D) Response profiles of P steroid-sensitive neurons in the MOE (24 cells, 7 slices; response intensities are coded by a color gradient). (E) Response profiles of P steroid-sensitive neurons in the VNO (25 cells, 5 slices). (F) Response profiles of E steroid-sensitive neurons in the MOE (15 cells, 7 slices). (G) Percentage of observed responses to individual sulfated steroids. P steroids showed a similar trend between MOE and VNO, with all three steroids eliciting between 20 and 40% of the total responses. A different trend was detected for E steroids, with one compound of the mixture (E0588) eliciting more than half (~60%) of the observed responses. (H) Venn diagram showing groups of P mix responsive neurons in the MOE. The majority of the neurons (13 cells) responded to all three components of the mixture. (I) Venn diagram showing groups of P mix responsive neurons in the VNO. The two main groups (9 and 8 cells) include neurons responding to two and three chemicals of the P mix. (J) Venn diagram showing groups of E mix responsive neurons in the MOE. The largest group (8 cells) contains neurons responding to only one chemical in the mixture, namely E0588.
Mentions: We applied the individual components of the P and E mix (see Materials and Methods and Supplementary Table 1) in addition to the mixtures to obtain response profiles of individual neurons of the VNO and the MOE (Figure 5A). Similar responses for the P mix sulfated steroids were obtained in cells of the MOE and the VNO, i.e., in both epithelia most sensory neurons responded to more than one compound of the mixture. This suggests that sensory neurons in both olfactory subsystems are broadly tuned to P mix sulfated steroids (Figures 5D,E). None of the P mix compounds was detected with much higher frequency than the others (Figure 5G). In contrast, the response profiles for E mix steroids in the MOE showed a different trend. One specific compound, i.e., E0588, activated the large majority of cells. The other two compounds were less effective (Figures 5F,G). The Venn diagrams in Figures 5H–J emphasize the above findings. Overall, the average number of P and E mix-sensitive cells in the MOE and the VNO varied considerably (MOE: 5 P mix cells vs. 1.7 E mix cells/slice; VNO: 2.3 P mix cells vs. 0.16 E mix cells/slice; for absolute numbers see Figure 1). E mix-responsive cells in the VNO were too rare (5 cells in 32 slices) to perform a systematic analysis of exact response profiles.

Bottom Line: Chemical communication is widespread in amphibians, but if compared to later diverging tetrapods the available functional data is limited.Furthermore, we found that larval and adult animals excrete multiple sulfated compounds with physical properties consistent with sulfated steroids.Breeding tadpole and frog water including these compounds activated a large subset of sensory neurons that also responded to synthetic steroids, showing that sulfated steroids are likely to convey intraspecific information.

View Article: PubMed Central - PubMed

Affiliation: Institute of Neurophysiology and Cellular Biophysics, University of Göttingen Göttingen, Germany ; Center for Nanoscale Microscopy and Molecular Physiology of the Brain Göttingen, Germany.

ABSTRACT
Chemical communication is widespread in amphibians, but if compared to later diverging tetrapods the available functional data is limited. The existing information on the vomeronasal system of anurans is particularly sparse. Amphibians represent a transitional stage in the evolution of the olfactory system. Most species have anatomically separated main and vomeronasal systems, but recent studies have shown that in anurans their molecular separation is still underway. Sulfated steroids function as migratory pheromones in lamprey and have recently been identified as natural vomeronasal stimuli in rodents. Here we identified sulfated steroids as the first known class of vomeronasal stimuli in the amphibian Xenopus laevis. We show that sulfated steroids are detected and concurrently processed by the two distinct olfactory subsystems of larval Xenopus laevis, the main olfactory system and the vomeronasal system. Our data revealed a similar but partially different processing of steroid-induced responses in the two systems. Differences of detection thresholds suggest that the two information channels are not just redundant, but rather signal different information. Furthermore, we found that larval and adult animals excrete multiple sulfated compounds with physical properties consistent with sulfated steroids. Breeding tadpole and frog water including these compounds activated a large subset of sensory neurons that also responded to synthetic steroids, showing that sulfated steroids are likely to convey intraspecific information. Our findings indicate that sulfated steroids are conserved vomeronasal stimuli functioning in phylogenetically distant classes of tetrapods living in aquatic and terrestrial habitats.

No MeSH data available.