Schreihofer AM, Stornetta RL, Guyenet PG (2000) Regulation of sympathetic vasomotor tone and arterial pressure by the rostral ventrolateral medulla after elimination of C1 neurons in rat. Neuroscience 2000 Abstracts 310.7. Society for Neuroscience, New Orleans, LA.
Summary: The rostral ventrolateral medulla (RVLM) tonically stimulates sympathetic preganglionic neurons to maintain arterial pressure (AP). Although the C1 neurons in the RVLM may have a sympathoexcitatory function, it is not known whether they are the essential presympathetic RVLM neurons. In the present study, we selectively destroyed spinally projecting C1 cells (∼84%) with bilateral microinjections (spinal segments T2-T3) of an anti-dopamine-betahydroxylase antibody conjugated to saporin (anti-DβH-SAP). 3-5 weeks later these rats had a normal AP and splanchnic nerve activity (SNA) under chloralose anesthesia. Extracellular recording and juxtacellular labeling of bulbospinal barosensitive neurons in RVLM revealed that after anti-DβH-SAP only the lightly myelinated RVLM neurons with no or very low levels of tyrosine hydroxylase immunoreactivity were preserved. In these rats, inhibition of RVLM (muscimol 100 pmol/100 nl/side) eliminated SNA and decreased AP as seen in control rats. However, treatment with anti-DβHSAP reduced the sympathoexcitatory and pressor responses to electrical stimulation in RVLM. Although treatment with anti-DβH-SAP also eliminated A5 noradrenergic cells, rats with selective lesions of A5 cells (local microinjection of 6-hydroxydopamine) displayed no deficits to stimulation of the RVLM. These data suggest basal sympathetic vasomotor tone relies primarily on non-catecholaminergic presympathetic cells in the RVLM. In contrast, bulbospinal adrenergic neurons are important for the increased SNA and AP produced by stimulation of the RVLM.
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