Synaptic and Non-Synaptic Control of Membrane Potential Fluctuations in Bulbar Respiratory Neurons of Cats
Bulbar respiratory neurons display rhythmic fluctuations of membrane potential in synchrony with the respiratory cycle. These undulatory potentials are largely dependent upon the periodically arriving synaptic activities. Intrinsic membrane properties also play a certain important role in the generation or modulation of these potentials. Several types of ionic conductance have been demonstrated in the presumed respiration-related neurons in the brainstem slices2, 3. However, since these neurons in tissue slices usually lack the spontaneous rhythmic modulation in membrane potential, the identification of the neuron type based upon the spontaneous patterns of firing and membrane potential fluctuations is yet uncertain. Moreover, it is hard to know at what timing any specific ionic conductance becomes active in the respiratory cycle change in membrane potential observed in different types of the respiratory neuron. Nonetheless, an intact brainstem preparation has also an inherent drawback to exclude the contamination of ionic currents mediated by action potentials and postsynaptic potentials4, 5. The coaxial multi-barrelled microelectrode technique6 can partly overcome these difficulties as it allows an in vivo intracellular recording of membrane potential in conjunction with an extracellular iontophoresis of drugs which could block action potentials and synaptic waves in the recorded neuron. The present study was aimed at elucidating the possible synaptic and non-synaptic mechanisms by which the periodic fluctuations of membrane potential are shaped in bulbar respiratory neurons of the ventral respiratory group.
KeywordsCadmium Citrate Glycine Respiration NMDA
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- 4.D.W. Richter, D. Ballantyne and S. Mifflin, Interaction between postsynaptic activities and membrane properties in medullary respiratory neurones, in: “Neurogenesis of Central Respiratory Rhythm,” A.L. Bianchi and M. Denavit-Saubie, ed., MTP, Lancaster, p 172(1985).Google Scholar
- 5.D.W. Richter, J. Champagnat and S. Mifflin, Membrane properties involved in respiratory rhythm generation, in: “Neurobiology of the Control of Breathing,” C. von Euler and H. Lagercrantz, ed., Raven, New York, p 141(1987).Google Scholar
- 8.R. Takeda, A. Haji, J.E. Remmers and T. Hukuhara, Respiratory pattern generation in the ventral respiratory group neurons, in: “Control of Breathing and Dyspnea,” T. Takishima and N.S. Cherniack, ed., Pergamon, Oxford, p65(1991).Google Scholar
- 10.R. Liinas and Y. Yarom, Properties and distribution of ionic conductances generating electroresponsiveness of mammalian inferior olivary neurones in vitro, J. Physiol. (Lond.), 315:569(1981).Google Scholar
- 11.P.M. Headley and S. Grillner, Excitatory amino acids and synaptic transmission: the evidence for a physiological function, TiPS Special Report 1991, Elsevier, Cambridge, p30(1991).Google Scholar