N-methyl-D-aspartate receptor subunit phenotypes of vagal afferent neurons in nodose ganglia of the rat

Abstract

Most vagal afferent neurons in rat nodose ganglia express mRNA coding for the NR1 subunit of the heteromeric N-methyl-D-aspartate (NMDA) receptor ion channel. NMDA receptor subunit immunoreactivity has been detected on axon terminals of vagal afferents in the dorsal hindbrain, suggesting a role for presynaptic NMDA receptors in viscerosensory function. Although NMDA receptor subunits (NR1, NR2B, NR2C, and NR2D) have been linked to distinct neuronal populations in the brain, the NMDA receptor subunit phenotype of vagal afferent neurons has not been determined. Therefore, we examined NMDA receptor subunit (NR1, NR2B, NR2C, and NR2D) immunoreactivity in vagal afferent neurons. We found that, although the left nodose contained significantly more neurons (7,603), than the right (5,978), the proportions of NMDA subunits expressed in the left and right nodose ganglia were not significantly different. Immunoreactivity for NMDA NR1 subunit was present in 92.3% of all nodose neurons. NR2B immunoreactivity was present in 56.7% of neurons; NR2C-expressing nodose neurons made up 49.4% of the total population; NR2D subunit immunoreactivity was observed in just 13.5% of all nodose neurons. Double labeling revealed that 30.2% of nodose neurons expressed immunoreactivity to both NR2B and NR2C, whereas NR2B and NR2D immunoreactivities were colocalized in 11.5% of nodose neurons. NR2C immunoreactivity colocalized with NR2D in 13.1% of nodose neurons. Our results indicate that most vagal afferent neurons express NMDA receptor ion channels composed of NR1, NR2B, and NR2C subunits and that a minority phenotype that expresses NR2D also expresses NR1, NR2B, and NR2C.

Reduction of food intake by cholecystokinin requires activation of hindbrain NMDA-type glutamate receptors

“…Circumstantial evidence continues to suggest a possible contribution to CCK-induced reduction of feeding by peripheral NMDA receptors. As mentioned above, virtually all vagal afferent neurons, including those that innervate the upper GI tract, express NMDA receptor subunit immunoreactivity (12,13). Furthermore, electrical activity recorded from the distal ends of cut vagal afferents is modulated by NMDA receptors (42), suggesting that receptors in peripheral vagal afferent membranes may participate in relaying sensory information to the brain.…”

“…However, they do not provide any information regarding the localization of NMDA receptors that participate in CCK-induced reduction of food intake. This issue is not trivial because NMDA receptors are expressed by vagal afferent neurons in the nodose ganglia (12,13), as well as by central vagal afferent terminals and postsynaptic neurons in the NTS (1). Moreover, electrophysiological experiments suggest that peripheral NMDA receptors may modulate gastrointestinal vagal afferent activity (42).…”

Capsaicin-induced neuronal death and proliferation of the primary sensory neurons located in the nodose ganglia of adult rats

“…DAPI labeled neuronal nuclear profiles were easily discriminated from glia nuclei by virtue of their large size and spherical shape and one or two nucleoli shadows. Control of DAPI staining was based on our previous study of NG neurons (Czaja et al, 2006).…”

“…In order to determine the total number of neurons in the NG, we counted DAPI labeled neuronal nuclear profiles under × 200 magnification in all of the sections for all series from a given ganglion and numbers were corrected for split nuclei as previously described (Czaja et al, 2006). The number of positive-stained neuronal profiles for particular antigen was counted using Axio Vision 4.6 Imaging system in every third section of the ganglion to eliminate the likelihood of counting the same neuron twice.…”

Coupling of Neuronal Nitric Oxide Synthase to NMDA Receptors via Postsynaptic Density-95 Depends on Estrogen and Contributes to the Central Control of Adult Female Reproduction

“…Sheep polyclonal antinNOS (1:3000) was a generous gift from Dr. P. C. Emson (Medical Research Council, Laboratory for Molecular Research, Cambridge, UK) (Herbison et al, 1996). Rabbit polyclonal anti-nNOS (61-700; 1:250) and anti-NR2B (71-8600; 1:500) were purchased from Zymed, described by Christopherson et al (1999), and previously characterized for immunocytochemistry by others (El-Husseini et al, 2000;Burette et al, 2002;Czaja et al, 2006). Monoclonal anti-PSD-95 (MA1-045; 1:400) was purchased from Affinity BioReagents.…”