Anatomical evidence that hypertension associated with the defence reaction in the cat is mediated by a direct projection from a restricted portion of the midbrain periaqueductal grey to the subretrofacial nucleus of the medulla

P. Carrive, R. Bandler*, R. A L Dampney

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

120 Citations (Scopus)

Abstract

Wheat germ agglutinin-horseradish peroxidase (WGA-HRP) injections were made at sites within a restricted portion of the midbrain periaqueductal grey region (PAG) of the cat at which microinjection of the excitant amino acid, d,l-homocysteic acid, elicits the strongest form of a defence reaction, including a hypertensive response. Among the revealed projections, significant anterograde labelling was found in a discrete region of the rostral ventrolateral medulla, the subretrofacial nucleus (SRF). In the cat, the SRF contains pressor neurones which project to the spinal preganglionic sympathetic outflow. The labelling was most marked ipsilaterally, although substantial contralateral labelling was also observed. To verify that the projection to the SRF originated from the restricted 'defence region' of the PAG, WGA-HRP or rhodamine-labelled microspheres were injected into physiologically-identified sites in the SRF. In all experiments, labelled neurones were found in the same restricted region of the PAG at which DLH injection evokes hypertension and behavioural signs of the defence reaction. The results are consistent with the hypothesis that a discrete cell group within the PAG mediates both somatic and autonomic components of the defence reaction and that the characteristic hypertensive response is mediated by a direct pathway from these PAG cells to pressor neurones in the SRF.

Original languageEnglish
Pages (from-to)339-345
Number of pages7
JournalBrain Research
Volume460
Issue number2
DOIs
Publication statusPublished - 20 Sep 1988
Externally publishedYes

Keywords

  • Blood pressure
  • Defence reaction
  • Excitatory amino acid
  • Hypertension
  • Midbrain periaqueductal grey
  • Rostral ventrolateral medulla
  • Subretrofacial nucleus

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