Bilateral nasal vascular responses to unilateral sympathetic stimulation.

Unilateral preganglionic cervical sympathetic stimulation in the anaesthetized cat evoked vasoconstriction in both nasal cavities, dependent on stimulation frequency. Vasoconstriction in the contralateral cavity was 15--20% of that of the stimulated side. Similar findings were obtained on unilateral Vidian nerve stimulation. Vasoconstriction evoked in the sympathectomized nasal cavity by stimulating the opposite cervical chain was reduced but not abolished by sectioning the posterior nasal and ethmoidal nerves of the stimulated side. It is suggested that vasoconstrictor fibres reach the opposite cavity either in these nerves or by way of blood vessels, but more likely that sympathetic fibres from these pathways innervate blood vessels which supply both nasal cavities.