Cervical spinal cord neurons receiving sensory input from the cranial vasculature.

The superior sagittal sinus, middle meningeal artery or superficial temporal artery was stimulated electrically in anaesthetized cats. Field potential recordings were used to locate areas of maximum responses in the upper cervical cord, which were then further examined for responsive single units. Short latency units responded to stimulation of the superior sagittal sinus with a mean latency of 11.9 ms. Some units also responded at longer latencies in the 200-250 ms range. Spontaneous discharge rates of some units in a dorsolateral area of the cervical cord were accelerated by iontophoretic application of glutamic or homocysteic acid to these same units. Evoked action potentials were commonly multiphasic. Dorsolateral area units commonly received convergent input from two vessels and often had receptive fields on the face and limbs. Spontaneously active cells which respond to electrical stimulation were accelerated by the local application of bradykinin to the sinus and responses of dorsolateral area units could be reversibly blocked by local application of lignocaine to the sinus. It was concluded that the dorsolateral area is a relay area for the perception of pain from cranial vessels.