Large-conductance calcium-activated potassium channels in the neurons of pre-Bötzinger complex and their participation in the regulation of central respiratory activity in neonatal rats.

The present study was conducted to test our hypothesis that the large-conductance calcium-activated potassium channels (BK(Ca) channels) exist in the neurons of the pre-Bötzinger complex (PBC), a brainstem region that may generate respiratory rhythm in mammals, and play roles in central regulation of respiratory activity in neonatal rats. Immunohistochemical technique revealed that BK(Ca) channels expressed in the neurons of PBC region. Whole cell voltage clamp recordings from the neurons in the PBC showed that BK(Ca) channels could be activated by membrane depolarization and blocked by 1mM tetraethylammonium (TEA) or 10microM paxilline in the preparation of thin (about 300microm) medullary slices of neonatal rats. The rhythmic respiratory-like discharge of hypoglossal rootlets could be changed by perfusing the thick (700-900microm) medullary slices with 1mM TEA or 10microM paxilline. Both TEA and paxilline could prolong the inspiratory duration, shorten the expiratory duration and increase the respiratory frequency. The results suggest that BK(Ca) channels exist in the PBC neurons and may be involved in the central control of rhythmic respiration in the neonatal rats.