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Firing properties of respiratory rhythm generating neurons in the absence of synaptic transmission in rat medulla in vitro

Experimental Brain Research volume 76, pages 530–536 (1989)Cite this article

Summary

It has previously been demonstrated that Pre-I neurons, localized in the rostral ventrolateral medulla, are important in the generation of the primary respiratory rhythm in brainstemspinal cord preparations from newborn rats. To investigate whether or not Pre-I neurons have endogenous pacemaker properties, we examined Pre-I neuron activity before and after chemical synaptic transmission was blocked by incubation in a low Ca2+ (0.2 mM), high Mg2+ (5 mM) solution (referred to here as low Ca). After incubation for about 30 min in low Ca, 28 (52%, type-1) out of 54 neurons tested in 27 preparations retained apparent rhythmic (phasic) activity after complete disappearance of C4 inspiratory activity. Sixteen neurons (30%, type-2) fired tonically and 10 (18%, type-3) were silent. We examined the effects of synaptic blockade on 14 inspiratory neurons in the RVL. The firing of all 14 neurons in 9 preparations disappeared concomitantly with the disappearance of C4 activity in low Ca. When the pH of the low Ca solution was lowered with a decrease in NaHCO3 concentration from 7.4 to 7.1, the firing rate of the Pre-I neurons (type-1) increased from 12 to 18/min. In conclusion, the generator of respiratory rhythm in the newborn rat is probably a neuronal network with chemical synapses that functions mainly through the endogenous Pre-I pacemaker cells. Intrinsic chemoreception in the rhythm generator is probably important in frequency control of respiratory rhythm.

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Affiliations

  1. Department of Physiology, Showa University School of Medicine, 1-5-8 Hatanodai, Shinagawa-ku, 142, Tokyo, Japan

    H. Onimaru, A. Arata & I. Homma

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  1. H. Onimaru
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  2. A. Arata
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  3. I. Homma
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Onimaru, H., Arata, A. & Homma, I. Firing properties of respiratory rhythm generating neurons in the absence of synaptic transmission in rat medulla in vitro. Exp Brain Res 76, 530–536 (1989). https://doi.org/10.1007/BF00248909

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  • DOI: https://doi.org/10.1007/BF00248909

Key words

  • Respiratory rhythm
  • Pacemaker cells
  • Central chemoreception
  • Newborn rat