Calcium-dependent conductances control neurones involved in termination of inspiration in cats.

Intracellular injection of the calcium chelator BAPTA into postinspiratory (PI) and late inspiratory neurones (late-I) of the ventral respiratory group of anaesthetised cat was performed to study the role of intracellular free calcium in patterning the activity of neurones controlling termination of inspiration. BAPTA injection into neurones resulted in an increase of input resistance and prolongation of action potential discharge with reduced adaptation. In addition, late-I neurones developed a secondary burst of action potentials during the postinspiratory phase of the cycle. We conclude that intracellular free calcium controls (1) the duration of activation and the degree of adaptation of PI neurones and (2) repolarisation of late-I neurones during postinspiration.