Calcium currents and calcium-dependent potassium currents in mammalian medullary respiratory neurones

• Published in: The Journal of physiology Vol. 470; no. 1; pp. 23 - 33
• Main Authors: Richter, D W, Champagnat, J, Jacquin, T, Benacka, R
• Format: Journal Article
• Language: English
• Published: Oxford The Physiological Society 01-10-1993; Blackwell
• Subjects: Action Potentials - drug effects; Action Potentials - physiology; Animals; Biological and medical sciences; Calcium - physiology; Calcium Channels - drug effects; Calcium Channels - physiology; Cats; Female; Fundamental and applied biological sciences. Psychology; Male; Medulla Oblongata - cytology; Medulla Oblongata - physiology; Membrane Potentials - drug effects; Membrane Potentials - physiology; Motor control and motor pathways. Reflexes. Control centers of vegetative functions. Vestibular system and equilibration; Neurons - physiology; Potassium Channels - drug effects; Potassium Channels - physiology; Rats; Rats, Wistar; Respiratory Mechanics - physiology; Respiratory Physiological Phenomena; Respiratory System - innervation; Tetraethylammonium Compounds - pharmacology; Tetrodotoxin - pharmacology; Vertebrates: nervous system and sense organs; Calcium; Electrical properties; Brain stem; Central nervous system; Discharge pattern; Electrophysiology; Ionic current; Vertebrata; Mammalia; Oscillation; Membrane potential; Respiratory control; Respiration; Brain (vertebrata)
• ISSN: 0022-3751; 1469-7793
• DOI: 10.1113/jphysiol.1993.sp019844

1. Respiratory neurons of mammals are rhythmically active because their membrane potential fluctuates periodically over a
voltage range of -70 to -55 mV. These respiratory drive potentials lead to periodic discharges of bursts of action potentials
lasting for 1-2 s. The neuronal processes stabilizing this rhythmic activity involve excitatory and inhibitory synaptic processes
that interact with specific membrane properties of the postsynaptic neurones. In the present experiments, performed on dorsal
and ventral groups of respiratory neurones under in vivo and in vitro conditions, we verified the modulating feature of such
intrinsic neuronal properties. 2. Intrinsic neuronal properties involve Ca2+ mechanisms that lead to intracellular Ca2+ accumulation,
and consequently to activation of Ca(2+)-dependent K+ currents. 3. Blockade of intracellular Ca2+ accumulation significantly
changed the amplitude and pattern of respiratory drive potentials, and blocked initial hyperpolarizing shifts of the membrane
potential following each period of synaptic activation. 4. The data demonstrate that postsynaptic activities and action potential
discharges activate low and high voltage-activated Ca2+ currents leading to intracellular Ca2+ accumulation and to activation
of Ca(2+)-dependent K+ currents that significantly modulate the voltage response of medullary respiratory neurones to on-going
synaptic activation. These intrinsic membrane properties also seem to be involved in the processes controlling termination
of rhythmic burst discharges.