Brain-derived neurotrophic factor-immunoreactive neurons in the rat vagal and glossopharyngeal sensory ganglia; co-expression with other neurochemical substances.

Immunohistochemistry for brain-derived neurotrophic factor (BDNF) was performed on the rat vagal and glossopharyngeal sensory ganglia. In the jugular, petrosal and nodose ganglia, 56.1+/-5.5%, 52.4+/-9.4% and 80.0+/-3.0% of sensory neurons, respectively, were immunoreactive for BDNF. These neurons were small- to medium-sized and observed throughout the ganglia. In the solitary tract nucleus, the neuropil showed BDNF immunoreactivity. A double immunofluorescence method demonstrated that BDNF-immunoreactive neurons were also immunoreactive for calcitonin gene-related peptide (CGRP), P2X3 receptor, the capsaicin receptor (VR1) or vanilloid receptor 1-like receptor (VRL-1) in the jugular (CGRP, 43.5%; P2X3 receptor, 51.1%; VR1, 71.7%; VRL-1, 0.5%), petrosal (CGRP, 33.2%; P2X3 receptor, 58.4%; VR1, 54.2%; VRL-1, 23.3%) and nodose ganglia (CGRP, 1.8%; P2X3 receptor, 49.1%; VR1, 70.7%; VRL-1, 11.5%). The co-expression with tyrosine hydroxylase was also detected in the petrosal (2.9%) and nodose ganglia (2.2%). However, BDNF-immunoreactive neurons were devoid of parvalbumin in these ganglia. The present findings suggest that BDNF-containing vagal and glossopharyngeal sensory neurons have nociceptive and chemoreceptive functions.

Comparison of capsaicin-evoked calcium transients between rat nodose and jugular ganglion neurons.

The objectives of this study were to describe the size distribution of capsaicin-sensitive neurons in nodose and jugular ganglia and to determine whether there is a difference in capsaicin sensitivity between these two types of ganglia. Functional identification was made by measurement of the capsaicin-evoked calcium (Ca2+) transients in cultured vagal sensory neurons of young adult Sprague-Dawley rats using the Fura-2-based ratiometric imaging technique. In the first study series, cells on the second day of culture were perfused with capsaicin solution (10(-7) M) for 15 s, and the Ca2+ transients were continuously recorded before, during, and after the capsaicin challenge. Out of 603 viable neurons, 57.5% were capsaicin-sensitive; the percentages of capsaicin-sensitive cells in the nodose and jugular ganglia were 59.8% and 55.4%, respectively. Capsaicin sensitivity predominated in the small- and medium-sized neurons; the capsaicin-sensitive cells generally had a diameter less than 35 microm in both types of ganglia. Although the results did not indicate any differences in the size distribution of capsaicin-sensitive neurons between the two ganglia, results of our second study series showed that a near-maximal concentration of capsaicin (3 x 10(-6) M) evoked a significantly greater peak Ca2+ transient in jugular neurons (382.5 +/- 85.5 nM) than in nodose neurons (134.3 +/- 17.5 nM). In summary, our results showed that an increase in cell diameter was accompanied by a decreasing trend in percentage of capsaicin-sensitive neurons in both vagal ganglia. Capsaicin at high concentration evoked a greater peak Ca2+ transient in jugular ganglion neurons, despite no difference in the responses to KCl between these two types of ganglion neurons.