Control of sympathetic vasomotor tone by catecholaminergic C1 neurones of the rostral ventrolateral medulla oblongata

May 6, 2011Cardiovascular research

Regulation of sympathetic nerve signals controlling blood vessel constriction by specific brainstem neurons

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Abstract

Acute inhibition of 50% of the C1 neuronal population in rats resulted in a ∼50% reduction in renal sympathetic nerve activity and a ∼25 mmHg drop in arterial blood pressure.

C1 neurones play a significant role in regulating sympathetic vasomotor tone and arterial blood pressure.
Systemic hypercapnia triggered strong sympathetic responses that were not influenced by the inhibition of C1 neurones.
Inhibition of C1 neurones led to a temporary decrease in perfusion pressure and reduced respiratory-related sympathetic nerve activity.

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AIMS: Increased sympathetic tone in obstructive sleep apnoea results from recurrent episodes of systemic hypoxia and hypercapnia and might be an important contributor to the development of cardiovascular disease. In this study, we re-evaluated the role of a specific population of sympathoexcitatory catecholaminergic C1 neurones of the rostral ventrolateral medulla oblongata in the control of sympathetic vasomotor tone, arterial blood pressure, and hypercapnia-evoked sympathetic and cardiovascular responses.

METHODS AND RESULTS: In anaesthetized rats in vivo and perfused rat working heart brainstem preparations in situ, C1 neurones were acutely silenced by application of the insect peptide allatostatin following cell-specific targeting with a lentiviral vector to express the inhibitory Drosophila allatostatin receptor. In anaesthetized rats with denervated peripheral chemoreceptors, acute inhibition of 50% of the C1 neuronal population resulted in ∼50% reduction in renal sympathetic nerve activity and a profound fall in arterial blood pressure (by ∼25 mmHg). However, under these conditions systemic hypercapnia still evoked vigorous sympathetic activation and the slopes of the CO(2)-evoked sympathoexcitatory and cardiovascular responses were not affected by inhibition of C1 neurones. Inhibition of C1 neurones in situ resulted in a reversible fall in perfusion pressure and the amplitude of respiratory-related bursts of thoracic sympathetic nerve activity.

CONCLUSION: These data confirm a fundamental physiological role of medullary catecholaminergic C1 neurones in maintaining resting sympathetic vasomotor tone and arterial blood pressure. However, C1 neurones do not appear to mediate sympathoexcitation evoked by central actions of CO(2).

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Control of sympathetic vasomotor tone by catecholaminergic C1 neurones of the rostral ventrolateral medulla oblongata

Abstract

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