Effects of stimulation of cervical sympathetic trunks with various frequencies on the local cortical cerebral blood flow measured by laser Doppler flowmetry in the rat.

The effects of electrical stimulation of cervical sympathetic trunks for 1-min duration at supramaximal intensity with various stimulus frequencies on local cortical cerebral blood flow were investigated in urethane-anesthetized rats. Electrical stimulation with low frequency (1-2 Hz) produced a significant increase in local cortical cerebral blood flow during the stimulation. The local cortical CBF reached 111% of the resting value during the stimulation at 10 Hz, and slightly decreased for about 30s after the end of stimulation. High-frequency stimulation (20-30 Hz) produced the short-term increase during the stimulation, which was followed by the dominant and long-lasting decrease, and the local cortical CBF reached 87% (at 30 Hz) of the resting value after the end of stimulation. The response of increase in flow was abolished by intravenous administration of beta adrenergic blocking agent (propranolol, 1.3 mg/kg i.v.), while the response of decrease in flow was abolished by alpha adrenergic blocking agent (phenoxybenzamine, 0.5 mg/kg i.v.).