A novel pressor area at the medullo-cervical junction that is not dependent on the RVLM: efferent pathways and chemical mediators.
Chemical stimulation of a region extending from the most caudal ventrolateral medulla into the upper cervical spinal cord evoked large sympathetically mediated pressor responses. These responses were not dependent on the integrity of the rostral ventrolateral medulla (RVLM) and may be mediated by glutamatergic neurons embedded in the white matter that project to the thoracic spinal cord. We term this new region the medullo-cervical pressor area (MCPA). This region is distinct from the caudal pressor area, because blockade of the RVLM with muscimol inhibited this pressor response but not that evoked from the MCPA. This is the first study to provide functional evidence for a cardiovascular role for neurons in the cervical spinal cord white matter that innervate sympathetic preganglionic neurons (Jansen and Loewy, 1997). Using retrograde tracing, in combination with immunohistochemistry and in situ hybridization, we identified two groups of spinally projecting neurons in the region. Approximately 50% of neurons in one group were excitatory because they contained vesicular glutamate transporter 1 (VGluT1)/VGluT2 mRNA, whereas the other contained a mixed population of neurons, some of which contained either VGluT1/VGluT2 or GAD67 (glutamic acid decarboxylase 67) mRNA. Despite the fact that activation of the MCPA causes potent sympathoexcitation, it does not act to restore arterial pressure after chemical lesion of the RVLM so that a role for this novel descending sympathoexcitatory region remains to be elucidated.
Seyedabadi
Maryam
M
Kolling Institute, Department of Neurosurgery, Royal North Shore Hospital, University of Sydney, School of Medical Sciences (Physiology), Sydney 2065, Australia.
Li
Qun
Q
Padley
James R
JR
Pilowsky
Paul M
PM
Goodchild
Ann K
AK
D000316:Adrenergic alpha-Agonists / Q000494:pharmacology; D000818:Animals; D001794:Blood Pressure / Q000502:physiology*; D004525:Efferent Pathways / Q000166:cytology / Q000378:metabolism*; D018755:GABA Agonists / Q000494:pharmacology; D005968:Glutamate Decarboxylase / Q000378:metabolism; D018698:Glutamic Acid / Q000378:metabolism* / Q000494:pharmacology; D007527:Isoenzymes / Q000378:metabolism; D008297:Male; D008526:Medulla Oblongata / Q000166:cytology / Q000378:metabolism*; D009118:Muscimol / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D013116:Spinal Cord / Q000166:cytology / Q000378:metabolism*; D013564:Sympathetic Nervous System / Q000166:cytology / Q000378:metabolism; D009435:Synaptic Transmission / Q000502:physiology; D014666:Vasomotor System / Q000502:physiology*; D050598:Vesicular Glutamate Transport Protein 1 / Q000235:genetics; D050599:Vesicular Glutamate Transport Protein 2 / Q000235:genetics
D000316:Adrenergic alpha-Agonists; D018755:GABA Agonists; D007527:Isoenzymes; C493475:Slc17a6 protein, rat; C493466:Slc17a7 protein, rat; D050598:Vesicular Glutamate Transport Protein 1; D050599:Vesicular Glutamate Transport Protein 2; D009118:Muscimol; D018698:Glutamic Acid; D005968:Glutamate Decarboxylase; C402565:glutamate decarboxylase 1