• We are sorry, but NCBI web applications do not support your browser and may not function properly. More information
Logo of jphysiolThe Journal of Physiology SiteMembershipSubmissionJ Physiol
J Physiol. Sep 1978; 282: 365–374.
PMCID: PMC1282745

The baroreceptor input to cardiac vagal motoneurones

Abstract

1. A study has been made of twenty-three cardiac vagal motoneurones (c.v.m.s) in the nucleus ambiguus of chloralose-anaesthetized cats.

2. C.v.m.s were identified as described previously (McAllen & Spyer, 1978). They were either spontaneously active (five units) or induced to fire by the ionophoresis of DL-homocysteic acid (DLH). Evidence is presented that above threshold, the DLH dose is not critical for the ability to show a baroreceptor influence.

3. The influence of the baroreceptors was determined by plotting pulse-triggered histograms of c.v.m. activity. If the aortic baroreceptors were denervated, the pulse synchronous activity disappeared reversibly on carotid occlusion (eight out of eight cases). In five out of fifteen cells studied, when aortic baroreceptor pathways were intact, a small degree of cardiac modulation survived carotid occlusion.

4. Estimates of the central delay of the baroreceptor-vagal reflex were made by timing the c.v.m. response to both electrical stimulation of the sinus nerve and natural baroreceptor stimulation. When both methods were used on individual units, electrical stimulation invariably gave shorter values. Natural stimulation gave values that fell into two ranges (20-60 msec and 70-110 msec), suggesting the involvement of two pathways.

5. Using higher currents, four c.v.m.s were induced to fire tonically during inspiration. Their activity in this phase showed a cardiac rhythm just as during expiration. Similarly, they responded to sinus nerve stimulation throughout the respiratory cycle.

6. This result is discussed in relation to the observation of others that the baroreceptor-cardiac reflex is ineffective during inspiration. It is proposed that there is no need to invoke a `gate' early in the pathway but that this phenomenon and the present observations are best explained by summation of influences at the c.v.m. cell membrane.

Full text

Full text is available as a scanned copy of the original print version. Get a printable copy (PDF file) of the complete article (1.0M), or click on a page image below to browse page by page. Links to PubMed are also available for Selected References.

Selected References

These references are in PubMed. This may not be the complete list of references from this article.
  • Davidson NS, Goldner S, McCloskey DI. Respiratory modulation of barareceptor and chemoreceptor reflexes affecting heart rate and cardiac vagal efferent nerve activity. J Physiol. 1976 Jul;259(2):523–530. [PMC free article] [PubMed]
  • Gabriel M, Seller H. Interaction of baroreceptor afferents from carotid sinus and aorta at the nucleus tractus solitarii. Pflugers Arch. 1970;318(1):7–20. [PubMed]
  • Haymet BT, McCloskey DI. Baroreceptor and chemoreceptor influences on heart rate during the respiratory cycle in the dog. J Physiol. 1975 Mar;245(3):699–712. [PMC free article] [PubMed]
  • IRIUCHIJIMA J, KUMADA M. EFFERENT CARDIAC VAGAL DISCHARGE OF THE DOG IN RESPONSE TO ELECTRICAL STIMULATION OF SENSORY NERVES. Jpn J Physiol. 1963 Dec 15;13:599–605. [PubMed]
  • IRIUCHIJIMA J, KUMADA M. ACTIVITY OF SINGLE VAGAL FIBERS EFFERENT TO THE HEART. Jpn J Physiol. 1964 Oct 15;14:479–487. [PubMed]
  • JEWETT DL. ACTIVITY OF SINGLE EFFERENT FIBRES IN THE CERVICAL VAGUS NERVE OF THE DOG, WITH SPECIAL REFERENCE TO POSSIBLE CARDIO-INHIBITORY FIBRES. J Physiol. 1964 Dec;175:321–357. [PMC free article] [PubMed]
  • Katona PG, Lipson D, Dauchot PJ. Opposing central and peripheral effects of atropine on parasympathetic cardiac control. Am J Physiol. 1977 Feb;232(2):H146–H151. [PubMed]
  • Katona PG, Poitras JW, Barnett GO, Terry BS. Cardiac vagal efferent activity and heart period in the carotid sinus reflex. Am J Physiol. 1970 Apr;218(4):1030–1037. [PubMed]
  • KOEPCHEN HP, LUX HD, WAGNER PH. [Studies on time requirement and central development of the pressor receptor heart reflex]. Pflugers Arch Gesamte Physiol Menschen Tiere. 1961;273:413–430. [PubMed]
  • Kunze DL. Reflex discharge patterns of cardiac vagal efferent fibres. J Physiol. 1972 Apr;222(1):1–15. [PMC free article] [PubMed]
  • Lipski J, McAllen RM, Spyer KM. The sinus nerve and baroreceptor input to the medulla of the cat. J Physiol. 1975 Sep;251(1):61–78. [PMC free article] [PubMed]
  • Lopes OU, Palmer JF. Proposed respiratory 'gating' mechanism for cardiac slowing. Nature. 1976 Dec 2;264(5585):454–456. [PubMed]
  • McAllen RM, Spyer KM. The location of cardiac vagal preganglionic motoneurones in the medulla of the cat. J Physiol. 1976 Jun;258(1):187–204. [PMC free article] [PubMed]
  • McAllen RM, Spyer KM. Two types of vagal preganglionic motoneurones projecting to the heart and lungs. J Physiol. 1978 Sep;282:353–364. [PMC free article] [PubMed]
  • Morest DK. Experimental study of the projections of the nucleus of the tractus solitarius and the area postrema in the cat. J Comp Neurol. 1967 Aug;130(4):277–300. [PubMed]
  • Neil E, Palmer JF. Effects of spontaneous respiration on the latency of reflex cardiac chronotropic responses to baroreceptor stimulation. J Physiol. 1975 May;247(1):16P–16P. [PubMed]
  • SEARS TA. EFFERENT DISCHARGES IN ALPHA AND FUSIMOTOR FIBRES OF INTERCOSTAL NERVES OF THE CAT. J Physiol. 1964 Nov;174:295–315. [PMC free article] [PubMed]
  • WARNER HR, COX A. A mathematical model of heart rate control by sympathetic and vagus efferent information. J Appl Physiol. 1962 Mar;17:349–355. [PubMed]

Articles from The Journal of Physiology are provided here courtesy of The Physiological Society

Formats:

Related citations in PubMed

See reviews...See all...

Cited by other articles in PMC

See all...

Links

  • Compound
    Compound
    PubChem Compound links
  • PubMed
    PubMed
    PubMed citations for these articles
  • Substance
    Substance
    PubChem Substance links

Recent Activity

Your browsing activity is empty.

Activity recording is turned off.

Turn recording back on

See more...