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Transsynaptic transport of wheat germ agglutinin expressed in a subset of type II taste cells of transgenic mice.

Damak S, Mosinger B, Margolskee RF - BMC Neurosci (2008)

Bottom Line: WGA immunoreactivity was also found in the trigeminal ganglion, suggesting that T1r3-expressing cells make synapses with trigeminal neurons.WGA was not detected in the parabrachial nucleus, or the gustatory cortex.These results show the usefulness of genetically encoded WGA as a tracer for the first and second order neurons that innervate a subset of taste cells, but not for higher order neurons, and demonstrate that the main route of output from type II taste cells is the gustatory neuron, not the type III cells.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Physiology and Biophysics, Mount Sinai School of Medicine, 1425 Madison Avenue, Box 1677, New York, New York, 10029, USA. sami.damak@rdls.nestle.com

ABSTRACT

Background: Anatomical tracing of neural circuits originating from specific subsets of taste receptor cells may shed light on interactions between taste cells within the taste bud and taste cell-to nerve interactions. It is unclear for example, if activation of type II cells leads to direct activation of the gustatory nerves, or whether the information is relayed through type III cells. To determine how WGA produced in T1r3-expressing taste cells is transported into gustatory neurons, transgenic mice expressing WGA-IRES-GFP driven by the T1r3 promoter were generated.

Results: Immunohistochemistry showed co-expression of WGA, GFP and endogenous T1r3 in the taste bud cells of transgenic mice: the only taste cells immunoreactive for WGA were the T1r3-expressing cells. The WGA antibody also stained intragemmal nerves. WGA, but not GFP immunoreactivity was found in the geniculate and petrosal ganglia of transgenic mice, indicating that WGA was transported across synapses. WGA immunoreactivity was also found in the trigeminal ganglion, suggesting that T1r3-expressing cells make synapses with trigeminal neurons. In the medulla, WGA was detected in the nucleus of the solitary tract but also in the nucleus ambiguus, the vestibular nucleus, the trigeminal nucleus and in the gigantocellular reticular nucleus. WGA was not detected in the parabrachial nucleus, or the gustatory cortex.

Conclusion: These results show the usefulness of genetically encoded WGA as a tracer for the first and second order neurons that innervate a subset of taste cells, but not for higher order neurons, and demonstrate that the main route of output from type II taste cells is the gustatory neuron, not the type III cells.

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Immunohistochemistry of a transverse section of the medulla of a T1r3-WGA-IRES-GFP transgenic mouse (Bregma -6.25) stained for WGA. The entire section is shown in the insert in the middle of the figure (c), with black boxes showing the location of the high magnification pictures above (a) and below (d). Equivalent areas from a WT mouse are shown on the right (b,e). Higher magnification from the areas of panel c indicated by the white boxes are shown in panels f and g. Immunoreactivity for WGA is found in the NTS (n), the nucleus ambiguus (a), the vestibular nucleus (v), the trigeminal nucleus (Tr), and in the gigantocellular reticular nucleus (Gi) in the T1r3-WGA-IRES-GFP mouse but not in the WT mouse.
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Figure 4: Immunohistochemistry of a transverse section of the medulla of a T1r3-WGA-IRES-GFP transgenic mouse (Bregma -6.25) stained for WGA. The entire section is shown in the insert in the middle of the figure (c), with black boxes showing the location of the high magnification pictures above (a) and below (d). Equivalent areas from a WT mouse are shown on the right (b,e). Higher magnification from the areas of panel c indicated by the white boxes are shown in panels f and g. Immunoreactivity for WGA is found in the NTS (n), the nucleus ambiguus (a), the vestibular nucleus (v), the trigeminal nucleus (Tr), and in the gigantocellular reticular nucleus (Gi) in the T1r3-WGA-IRES-GFP mouse but not in the WT mouse.

Mentions: To determine if WGA was taken up by the second order neurons of the neural circuits that originate from the T1r3-expressing cells, we immunostained sections from the medulla of T1r3-WGA-IRES-GFP transgenic mice. As expected, WGA immunoreactivity was found in the nucleus of the solitary tract (NTS) but we also observed immunostaining in other areas of the medulla, including the nucleus ambiguus, the vestibular nucleus, the trigeminal nucleus and the gigantocellular reticular nucleus (Figure 4). The staining was weak but specific since no WGA immunoreactivity was observed in sections from equivalent areas from non-transgenic mice processed in parallel and with the same incubation and development times. Under high magnification, one can clearly see cell bodies stained above background, and occasionally staining of a neurite between two cell bodies (Figure 4f). No GFP immunoreactivity was found in any part of the medulla. We were not able to detect any WGA immunoreactivity in more central (tertiary) areas along the gustatory neural circuits, including the parabrachial nucleus, and the gustatory cortex. This is not surprising as the signal from WGA weakens every time it crosses a synapse, and the WGA signal was faint in the NTS. These experiments were repeated three times with always the same results.


Transsynaptic transport of wheat germ agglutinin expressed in a subset of type II taste cells of transgenic mice.

Damak S, Mosinger B, Margolskee RF - BMC Neurosci (2008)

Immunohistochemistry of a transverse section of the medulla of a T1r3-WGA-IRES-GFP transgenic mouse (Bregma -6.25) stained for WGA. The entire section is shown in the insert in the middle of the figure (c), with black boxes showing the location of the high magnification pictures above (a) and below (d). Equivalent areas from a WT mouse are shown on the right (b,e). Higher magnification from the areas of panel c indicated by the white boxes are shown in panels f and g. Immunoreactivity for WGA is found in the NTS (n), the nucleus ambiguus (a), the vestibular nucleus (v), the trigeminal nucleus (Tr), and in the gigantocellular reticular nucleus (Gi) in the T1r3-WGA-IRES-GFP mouse but not in the WT mouse.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2571104&req=5

Figure 4: Immunohistochemistry of a transverse section of the medulla of a T1r3-WGA-IRES-GFP transgenic mouse (Bregma -6.25) stained for WGA. The entire section is shown in the insert in the middle of the figure (c), with black boxes showing the location of the high magnification pictures above (a) and below (d). Equivalent areas from a WT mouse are shown on the right (b,e). Higher magnification from the areas of panel c indicated by the white boxes are shown in panels f and g. Immunoreactivity for WGA is found in the NTS (n), the nucleus ambiguus (a), the vestibular nucleus (v), the trigeminal nucleus (Tr), and in the gigantocellular reticular nucleus (Gi) in the T1r3-WGA-IRES-GFP mouse but not in the WT mouse.
Mentions: To determine if WGA was taken up by the second order neurons of the neural circuits that originate from the T1r3-expressing cells, we immunostained sections from the medulla of T1r3-WGA-IRES-GFP transgenic mice. As expected, WGA immunoreactivity was found in the nucleus of the solitary tract (NTS) but we also observed immunostaining in other areas of the medulla, including the nucleus ambiguus, the vestibular nucleus, the trigeminal nucleus and the gigantocellular reticular nucleus (Figure 4). The staining was weak but specific since no WGA immunoreactivity was observed in sections from equivalent areas from non-transgenic mice processed in parallel and with the same incubation and development times. Under high magnification, one can clearly see cell bodies stained above background, and occasionally staining of a neurite between two cell bodies (Figure 4f). No GFP immunoreactivity was found in any part of the medulla. We were not able to detect any WGA immunoreactivity in more central (tertiary) areas along the gustatory neural circuits, including the parabrachial nucleus, and the gustatory cortex. This is not surprising as the signal from WGA weakens every time it crosses a synapse, and the WGA signal was faint in the NTS. These experiments were repeated three times with always the same results.

Bottom Line: WGA immunoreactivity was also found in the trigeminal ganglion, suggesting that T1r3-expressing cells make synapses with trigeminal neurons.WGA was not detected in the parabrachial nucleus, or the gustatory cortex.These results show the usefulness of genetically encoded WGA as a tracer for the first and second order neurons that innervate a subset of taste cells, but not for higher order neurons, and demonstrate that the main route of output from type II taste cells is the gustatory neuron, not the type III cells.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Physiology and Biophysics, Mount Sinai School of Medicine, 1425 Madison Avenue, Box 1677, New York, New York, 10029, USA. sami.damak@rdls.nestle.com

ABSTRACT

Background: Anatomical tracing of neural circuits originating from specific subsets of taste receptor cells may shed light on interactions between taste cells within the taste bud and taste cell-to nerve interactions. It is unclear for example, if activation of type II cells leads to direct activation of the gustatory nerves, or whether the information is relayed through type III cells. To determine how WGA produced in T1r3-expressing taste cells is transported into gustatory neurons, transgenic mice expressing WGA-IRES-GFP driven by the T1r3 promoter were generated.

Results: Immunohistochemistry showed co-expression of WGA, GFP and endogenous T1r3 in the taste bud cells of transgenic mice: the only taste cells immunoreactive for WGA were the T1r3-expressing cells. The WGA antibody also stained intragemmal nerves. WGA, but not GFP immunoreactivity was found in the geniculate and petrosal ganglia of transgenic mice, indicating that WGA was transported across synapses. WGA immunoreactivity was also found in the trigeminal ganglion, suggesting that T1r3-expressing cells make synapses with trigeminal neurons. In the medulla, WGA was detected in the nucleus of the solitary tract but also in the nucleus ambiguus, the vestibular nucleus, the trigeminal nucleus and in the gigantocellular reticular nucleus. WGA was not detected in the parabrachial nucleus, or the gustatory cortex.

Conclusion: These results show the usefulness of genetically encoded WGA as a tracer for the first and second order neurons that innervate a subset of taste cells, but not for higher order neurons, and demonstrate that the main route of output from type II taste cells is the gustatory neuron, not the type III cells.

Show MeSH
Related in: MedlinePlus