Modulation of BK channel activities by calcium-sensing receptor in rat bronchopulmonary sensory neurons.

This study was carried out to investigate the expression of large-conductance Ca(2+)-activated potassium (BK) channels and to explore the possible modulation of BK channel activities by calcium-sensing receptors (CaSR) in rat bronchopulmonary sensory neurons. The expression of BK channels was demonstrated by immunohistochemistry and RT-PCR. Results from whole-cell patch-clamp recordings demonstrated that activation of CaSR with its agonist spermine or NPS R-568 showed a dual regulating effect on BK channel activities: it potentiated BK currents in cells exhibiting low baseline BK activity while slightly inhibited BK currents in cells with high baseline BK activity. Blocking CaSR with its antagonist NPS 2143 significantly inhibited BK currents. Our results further showed that the modulation of BK currents by CaSR activation or blockade was completely abolished when the intracellular Ca(2+) was chelated by BAPTA-AM. In summary, our data suggest that CaSR plays an integrative role in bronchopulmonary afferent signaling, at least partially through the regulation of BK channel activities.

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.

Intimate apposition of the glomus and smooth muscle cells (g-s connection) in the carotid labyrinth of juvenile bullfrogs.

Intimate apposition of the glomus and smooth muscle cells (g-s connection) was found in almost all glomus cells of the carotid labyrinths in juvenile bullfrogs, Rana catesbeiana. There were three types of g-s connection: between thin processes (0.1-0.2 micron in width) without dense-cored vesicles of glomus cells and smooth muscle cells; between thick processes (1.0-1.5 microns in width) with dense-cored vesicles of glomus cells and smooth muscle cells; and between the tongue-like projections of smooth muscle cells and the flat surface of the glomus cell. In some cases, a single glomus cell made g-s connections with several smooth muscle cells. Exocytosis often occurs at the g-s connection. Afferent and efferent synapses were found on the glomus cells with g-s connections. Reciprocal synapses were also observed. On the basis of these findings, the second and third types of g-s connection are presumed to participate in vascular regulation.