Stimulation of the Superior Sagittal Sinus Increases Metabolic Activity and Blood Flow in Certain Regions of the Brainstem and Upper Cervical Spinal Cord of the Cat

To investigate the anatomical distribution of cells concerned with relaying craniovascular nociception, local cerebral blood flow was examined in the cat using the tracer 14C-iodoantipyrine and local cerebral glucose utilization determined by the 2-deoxyglucose method in tissue autoradiographs. The superior sagittal sinus was stimulated electrically and its effect on caudal brainstem and upper cervical spinal cord blood flow and metabolism evaluated. This caused increased metabolic activity and blood flow in the trigeminal nucleus caudalis, in the cervical dorsal horn and in a discrete area in the dorsolateral spinal cord at the second cervical segment. Responses in these 3 areas were blocked by ablation of the trigeminal ganglia. The dorsolateral area activated in the spinal cord corresponds to a group of cells in or near the lateral cervical nucleus that may form an important relay for craniovascular nociception and thus be of relevance to the mechanism of headache.