The peripheral pathway for extracranial vasodilatation in the cat.

The locus coeruleus was electrically stimulated in 27 cats with high spinal cord sections. Common carotid blood flow was measured using electromagnetic flow probes, and arterial resistance calculated from mean arterial blood pressure and flow. Activation of the locus coeruleus caused an ipsilateral decrease in common carotid resistance, an effect previously demonstrated to depend on the integrity of the facial nerve. This vasodilator response is now shown to be mediated approximately equally by the pterygopalatine (sphenopalatine) and otic ganglia.