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Bidirectional regulation of thermotaxis by glutamate transmissions in Caenorhabditis elegans.

Ohnishi N, Kuhara A, Nakamura F, Okochi Y, Mori I - EMBO J. (2011)

Bottom Line: EAT-4/VGLUT (vesicular glutamate transporter)-dependent glutamate signals from AFD thermosensory neurons inhibit the postsynaptic AIY interneurons through activation of GLC-3/GluCl inhibitory glutamate receptor and behaviourally drive migration towards colder temperature.By contrast, EAT-4-dependent glutamate signals from AWC thermosensory neurons stimulate the AIY neurons to induce migration towards warmer temperature.Alteration of the strength of AFD and AWC signals led to significant changes of AIY activity, resulting in drastic modulation of behaviour.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Molecular Neurobiology, Division of Biological Science, Department of Molecular Biology, Graduate School of Science, Nagoya University, Nagoya, Aichi, Japan.

ABSTRACT
In complex neural circuits of the brain, massive information is processed with neuronal communication through synaptic transmissions. It is thus fundamental to delineate information flows encoded by various kinds of transmissions. Here, we show that glutamate signals from two distinct sensory neurons bidirectionally affect the same postsynaptic interneuron, thereby producing the opposite behaviours. EAT-4/VGLUT (vesicular glutamate transporter)-dependent glutamate signals from AFD thermosensory neurons inhibit the postsynaptic AIY interneurons through activation of GLC-3/GluCl inhibitory glutamate receptor and behaviourally drive migration towards colder temperature. By contrast, EAT-4-dependent glutamate signals from AWC thermosensory neurons stimulate the AIY neurons to induce migration towards warmer temperature. Alteration of the strength of AFD and AWC signals led to significant changes of AIY activity, resulting in drastic modulation of behaviour. We thus provide an important insight on information processing, in which two glutamate transmissions encoding opposite information flows regulate neural activities to produce a large spectrum of behavioural outputs.

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Related in: MedlinePlus

Thermotaxis of eat-4(ky5) mutants. (A) Individual thermotaxis assay of wild-type and eat-4(ky5) mutant animals. Adult animals cultivated at 20°C were individually placed on a radial thermal gradient with 17°C at the centre and 25°C at the periphery (9 cm diameter), and were allowed to move freely for 60 min (see Supplementary data for details). Most wild-type animals leave striking isothermal tracks on the assay plate, whereas eat-4(ky5) mutants move randomly. (B) Fraction of wild-type and eat-4(ky5) mutant animals that moved isothermally in the individual thermotaxis assay; n=60 animals for both strains. Error bar indicates s.e.m. Double asterisk indicates P<0.01 in ANOVA for a comparison with wild-type animals. (C) Procedures for population thermotaxis assay using a linear temperature gradient (Ito et al, 2006). About 50–200 animals cultivated at 17, 20, or 23°C were placed on the agar surface of 20°C (origin) and allowed to move freely for 60 min. The steepness of the temperature gradient was stably kept at 0.45°C/cm during the assay. The thermotactic behaviour was quantified as TTX index (see Supplementary data for details). (D) Distributions of wild-type and eat-4(ky5) mutant animals cultivated at 17, 20, or 23°C in the population thermotaxis assay. (E) TTX indices of wild-type and eat-4(ky5) mutant animals. Red bars, yellow bars, and blue bars represent TTX indices of animals cultivated at 23, 20, and 17°C, respectively; n=3 or more assays. Error bar indicates s.e.m. Double asterisk indicates P<0.01 in post hoc Tukey–Kramer tests for a comparison with wild-type animals.
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f1: Thermotaxis of eat-4(ky5) mutants. (A) Individual thermotaxis assay of wild-type and eat-4(ky5) mutant animals. Adult animals cultivated at 20°C were individually placed on a radial thermal gradient with 17°C at the centre and 25°C at the periphery (9 cm diameter), and were allowed to move freely for 60 min (see Supplementary data for details). Most wild-type animals leave striking isothermal tracks on the assay plate, whereas eat-4(ky5) mutants move randomly. (B) Fraction of wild-type and eat-4(ky5) mutant animals that moved isothermally in the individual thermotaxis assay; n=60 animals for both strains. Error bar indicates s.e.m. Double asterisk indicates P<0.01 in ANOVA for a comparison with wild-type animals. (C) Procedures for population thermotaxis assay using a linear temperature gradient (Ito et al, 2006). About 50–200 animals cultivated at 17, 20, or 23°C were placed on the agar surface of 20°C (origin) and allowed to move freely for 60 min. The steepness of the temperature gradient was stably kept at 0.45°C/cm during the assay. The thermotactic behaviour was quantified as TTX index (see Supplementary data for details). (D) Distributions of wild-type and eat-4(ky5) mutant animals cultivated at 17, 20, or 23°C in the population thermotaxis assay. (E) TTX indices of wild-type and eat-4(ky5) mutant animals. Red bars, yellow bars, and blue bars represent TTX indices of animals cultivated at 23, 20, and 17°C, respectively; n=3 or more assays. Error bar indicates s.e.m. Double asterisk indicates P<0.01 in post hoc Tukey–Kramer tests for a comparison with wild-type animals.

Mentions: Two types of thermotaxis assays were performed for eat-4(ky5) mutants. The individual thermotaxis assay is suitable for scoring isothermal tracking (IT) behaviour (Figure 1A and B; Gomez et al, 2001). Although many wild-type animals (55±8%) exhibited IT behaviour in a radial thermal gradient from 17 to 25°C after cultivation at 20°C in well-fed conditions, no eat-4(ky5) mutants (0%) exhibited IT behaviour (Figure 1A and B). In addition, eat-4(ky5) mutants showed severe impairment in the population thermotaxis assay that is suitable for quantitatively assessing the migration ability towards the cultivation temperature (Figure 1C–E; Ito et al, 2006). After cultivation at 23, 20, or 17°C in well-fed condition, most of wild-type animals migrated up or down the linear temperature gradient (0.45°C/cm) until they reached the region nearly corresponding to the previous cultivation temperature (Figure 1C and D). However, eat-4(ky5) animals exhibited little tendency to migrate towards cultivation temperature and mostly dispersed in a wide area (Figure 1D). TTX indices (Figure 1C) of eat-4(ky5) mutants cultivated at both 23°C and 17°C (0.47±0.14 at 23°C and −1.46±0.08 at 17°C) differed significantly from those of wild-type animals (2.27±0.19 at 23°C and −2.96±0.22 at 17°C; Figure 1E). Although eat-4(ky5) mutants did not show locomotion defect, they dispersed less than wild-type animals in the absence of a temperature gradient (Supplementary Figure S2A and B; Ségalat et al, 1995), indicating the possibility that abnormal TTX indices of eat-4(ky5) mutants could result from other defects, such as local search defect. Nevertheless, eat-4(ky5) mutants dispersed more broadly from cultivation temperature than wild-type animals on a thermal gradient (Figure 1D). This tendency was also observed in the population thermotaxis assay of eat-4(ky5) mutants cultivated at 20°C after being placed at the higher and lower temperature positions in the gradient (Supplementary Figure S2C and D). These results suggest that eat-4(ky5) mutants indeed exhibit thermotaxis defect, implicating the behavioural regulation by EAT-4-dependent glutamatergic neurotransmission.


Bidirectional regulation of thermotaxis by glutamate transmissions in Caenorhabditis elegans.

Ohnishi N, Kuhara A, Nakamura F, Okochi Y, Mori I - EMBO J. (2011)

Thermotaxis of eat-4(ky5) mutants. (A) Individual thermotaxis assay of wild-type and eat-4(ky5) mutant animals. Adult animals cultivated at 20°C were individually placed on a radial thermal gradient with 17°C at the centre and 25°C at the periphery (9 cm diameter), and were allowed to move freely for 60 min (see Supplementary data for details). Most wild-type animals leave striking isothermal tracks on the assay plate, whereas eat-4(ky5) mutants move randomly. (B) Fraction of wild-type and eat-4(ky5) mutant animals that moved isothermally in the individual thermotaxis assay; n=60 animals for both strains. Error bar indicates s.e.m. Double asterisk indicates P<0.01 in ANOVA for a comparison with wild-type animals. (C) Procedures for population thermotaxis assay using a linear temperature gradient (Ito et al, 2006). About 50–200 animals cultivated at 17, 20, or 23°C were placed on the agar surface of 20°C (origin) and allowed to move freely for 60 min. The steepness of the temperature gradient was stably kept at 0.45°C/cm during the assay. The thermotactic behaviour was quantified as TTX index (see Supplementary data for details). (D) Distributions of wild-type and eat-4(ky5) mutant animals cultivated at 17, 20, or 23°C in the population thermotaxis assay. (E) TTX indices of wild-type and eat-4(ky5) mutant animals. Red bars, yellow bars, and blue bars represent TTX indices of animals cultivated at 23, 20, and 17°C, respectively; n=3 or more assays. Error bar indicates s.e.m. Double asterisk indicates P<0.01 in post hoc Tukey–Kramer tests for a comparison with wild-type animals.
© Copyright Policy - open-access
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC3094115&req=5

f1: Thermotaxis of eat-4(ky5) mutants. (A) Individual thermotaxis assay of wild-type and eat-4(ky5) mutant animals. Adult animals cultivated at 20°C were individually placed on a radial thermal gradient with 17°C at the centre and 25°C at the periphery (9 cm diameter), and were allowed to move freely for 60 min (see Supplementary data for details). Most wild-type animals leave striking isothermal tracks on the assay plate, whereas eat-4(ky5) mutants move randomly. (B) Fraction of wild-type and eat-4(ky5) mutant animals that moved isothermally in the individual thermotaxis assay; n=60 animals for both strains. Error bar indicates s.e.m. Double asterisk indicates P<0.01 in ANOVA for a comparison with wild-type animals. (C) Procedures for population thermotaxis assay using a linear temperature gradient (Ito et al, 2006). About 50–200 animals cultivated at 17, 20, or 23°C were placed on the agar surface of 20°C (origin) and allowed to move freely for 60 min. The steepness of the temperature gradient was stably kept at 0.45°C/cm during the assay. The thermotactic behaviour was quantified as TTX index (see Supplementary data for details). (D) Distributions of wild-type and eat-4(ky5) mutant animals cultivated at 17, 20, or 23°C in the population thermotaxis assay. (E) TTX indices of wild-type and eat-4(ky5) mutant animals. Red bars, yellow bars, and blue bars represent TTX indices of animals cultivated at 23, 20, and 17°C, respectively; n=3 or more assays. Error bar indicates s.e.m. Double asterisk indicates P<0.01 in post hoc Tukey–Kramer tests for a comparison with wild-type animals.
Mentions: Two types of thermotaxis assays were performed for eat-4(ky5) mutants. The individual thermotaxis assay is suitable for scoring isothermal tracking (IT) behaviour (Figure 1A and B; Gomez et al, 2001). Although many wild-type animals (55±8%) exhibited IT behaviour in a radial thermal gradient from 17 to 25°C after cultivation at 20°C in well-fed conditions, no eat-4(ky5) mutants (0%) exhibited IT behaviour (Figure 1A and B). In addition, eat-4(ky5) mutants showed severe impairment in the population thermotaxis assay that is suitable for quantitatively assessing the migration ability towards the cultivation temperature (Figure 1C–E; Ito et al, 2006). After cultivation at 23, 20, or 17°C in well-fed condition, most of wild-type animals migrated up or down the linear temperature gradient (0.45°C/cm) until they reached the region nearly corresponding to the previous cultivation temperature (Figure 1C and D). However, eat-4(ky5) animals exhibited little tendency to migrate towards cultivation temperature and mostly dispersed in a wide area (Figure 1D). TTX indices (Figure 1C) of eat-4(ky5) mutants cultivated at both 23°C and 17°C (0.47±0.14 at 23°C and −1.46±0.08 at 17°C) differed significantly from those of wild-type animals (2.27±0.19 at 23°C and −2.96±0.22 at 17°C; Figure 1E). Although eat-4(ky5) mutants did not show locomotion defect, they dispersed less than wild-type animals in the absence of a temperature gradient (Supplementary Figure S2A and B; Ségalat et al, 1995), indicating the possibility that abnormal TTX indices of eat-4(ky5) mutants could result from other defects, such as local search defect. Nevertheless, eat-4(ky5) mutants dispersed more broadly from cultivation temperature than wild-type animals on a thermal gradient (Figure 1D). This tendency was also observed in the population thermotaxis assay of eat-4(ky5) mutants cultivated at 20°C after being placed at the higher and lower temperature positions in the gradient (Supplementary Figure S2C and D). These results suggest that eat-4(ky5) mutants indeed exhibit thermotaxis defect, implicating the behavioural regulation by EAT-4-dependent glutamatergic neurotransmission.

Bottom Line: EAT-4/VGLUT (vesicular glutamate transporter)-dependent glutamate signals from AFD thermosensory neurons inhibit the postsynaptic AIY interneurons through activation of GLC-3/GluCl inhibitory glutamate receptor and behaviourally drive migration towards colder temperature.By contrast, EAT-4-dependent glutamate signals from AWC thermosensory neurons stimulate the AIY neurons to induce migration towards warmer temperature.Alteration of the strength of AFD and AWC signals led to significant changes of AIY activity, resulting in drastic modulation of behaviour.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Molecular Neurobiology, Division of Biological Science, Department of Molecular Biology, Graduate School of Science, Nagoya University, Nagoya, Aichi, Japan.

ABSTRACT
In complex neural circuits of the brain, massive information is processed with neuronal communication through synaptic transmissions. It is thus fundamental to delineate information flows encoded by various kinds of transmissions. Here, we show that glutamate signals from two distinct sensory neurons bidirectionally affect the same postsynaptic interneuron, thereby producing the opposite behaviours. EAT-4/VGLUT (vesicular glutamate transporter)-dependent glutamate signals from AFD thermosensory neurons inhibit the postsynaptic AIY interneurons through activation of GLC-3/GluCl inhibitory glutamate receptor and behaviourally drive migration towards colder temperature. By contrast, EAT-4-dependent glutamate signals from AWC thermosensory neurons stimulate the AIY neurons to induce migration towards warmer temperature. Alteration of the strength of AFD and AWC signals led to significant changes of AIY activity, resulting in drastic modulation of behaviour. We thus provide an important insight on information processing, in which two glutamate transmissions encoding opposite information flows regulate neural activities to produce a large spectrum of behavioural outputs.

Show MeSH
Related in: MedlinePlus