The role of the glycine sensitive area of the ventral medulla in cardiovascular responses to carotid chemoreceptor and peripheral nerve stimulation

Janice M. Marshall*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

13 Citations (Scopus)


The present study on cats anaesthetised with Althesin, which unlike more commonly used anaesthetics does not prevent reflex activation of the brain-stem defence areas, reaffirmed that carotid chemoreceptor stimulation and radial nerve stimulation can evoke the visceral components of the alerting stage of the defence response (visceral alerting response). This includes tachycardia, mesenteric vasoconstriction but vasodilatation in skeletal muscle which is not secondary to the hyperventilation. However, mild chemoreceptor stimulation which evoked but a weak hyperventilation elicited bradycardia and vasoconstriction is mesentery and in muscle i.e. a response comparable with that evoked by chemoreceptor stimulation under chloralose or barbiturate anaesthesia. This suggests that chemoreceptor stimulation can evoke two separate patterns of response, the visceral alerting response predominating when the defence areas are strongly activated. The efferent pathway from the defence areas is known to synapse in the 'glycine sensitive area' of the ventral medulla which contains neurones whose activity seems to provide the main sympatho-excitatory drive for normal arterial pressure. Bilateral application of glycine to that area produces a pronounced fall in arterial pressure, apnoea and greatly attenuates the response to defence area stimulation, the vasoconstrictor components being abolished. In the present study bilaterally applied glycine abolished the muscle vasodilatation of the visceral alerting response evoked by chemoreceptor and radial nerve stimulation but both stimuli evoked vasoconstriction in mesenteric and muscle vasculature at least until arterial pressure was very low. It is proposed that both chemoreceptor and peripheral nerve stimulation can activate the defence areas to produce a visceral alerting response which is relayed via neurones of the glycine sensitive area. However, so long as neurones in that region continue to provide some tonic sympatho-excitatory drive both these peripheral inputs can activate sympathetic vasoconstrictor fibres via pathways which do not synapse in the glycine sensitive area. Such vasoconstriction may be part of the response normally seen when chemoreceptor stimulation fails to activate the defence areas.

Original languageEnglish
Pages (from-to)225-231
Number of pages7
JournalPflügers Archiv European Journal of Physiology
Issue number2
Publication statusPublished - Feb 1986


  • Blood pressure
  • Cardiovascular regulation
  • Carotid chemoreceptors
  • Defence response
  • Nociceptor stimulation
  • Ventral medulla

ASJC Scopus subject areas

  • Physiology
  • Clinical Biochemistry
  • Physiology (medical)


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