Key result
Chemical stimulation of the medullo-cervical pressor area evoked large sympathetically mediated pressor responses (60 mmHg increase in MAP) that were independent of the rostral ventrolateral medulla.
The study identifies a novel medullo-cervical pressor area (MCPA) that mediates potent sympathoexcitation and pressor responses independent of the rostral ventrolateral medulla.
Supports novel central sympathoexcitatory pathway in rodents; hypothesis-generating and should not yet alter clinical hypertension management.
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.
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Seyedabadi et al. (2006) studied Blood pressure regulation (n=35). Glutamate microinjection into the medullo-cervical pressor area (MCPA) vs. Baseline / RVLM blockade was evaluated on Change in mean arterial blood pressure (MAP). Chemical stimulation of the medullo-cervical pressor area evoked large sympathetically mediated pressor responses (60 mmHg increase in MAP) that were independent of the rostral ventrolateral medulla.
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