Lack of a role for substance P in the control of dural arterial flow.

The role of the neuropeptide substance P (SP) in the control of dural arterial blood flow was examined in barbiturate-anaesthetised rats. The parietal skull was trephinised and the blood flow in branches of the medial meningeal artery was monitored with a laser Doppler flowmeter. Electrical stimulation of the dura mater encephali at a parasagittal site with pulses of 0.5 ms (10-20 V, 5-10 Hz, 30 s) caused a transient increase in dural blood flow which was reproducible in size with repetitive stimulation. Neither the basal flow nor the stimulus-evoked flow was significantly changed by topical administration of SP, the SP analog septide, or the NK1 antagonist RP 67580. It is concluded that SP released from dural nerve fibres upon local stimulation does not play an important role in the regulation of dural arterial flow.