Vasoconstriction induced by inhalation of irritant vapour is associated with appearance of Fos protein in C1 catecholamine neurons in rabbit medulla oblongata.

The medulla oblongata was examined with Fos and tyrosine hydroxylase (TH) immunohistochemistry after 2 h of intermittent nasopharyngeal stimulation with formaldehyde vapour in the conscious rabbit. The stimulation caused apnoea, bradycardia and a rise in blood pressure known to be associated with vigorous vasoconstriction. Fos-positive neurons occurred in the spinal trigeminal nucleus, the nucleus tractus solitarius, the raphe nuclei and the ventrolateral medulla. In the rostral ventrolateral medulla, 68% of the Fos-positive neurons were TH-positive C1 cells. Our data indicate that nasopharyngeally-evoked peripheral vasoconstriction is associated with activation of C1 neurons.