Effect of acupuncture-like stimulation on cortical cerebral blood flow in anesthetized rats

Abstract

The effect of acupuncture-like stimulation of the forepaw on cortical cerebral blood flow (CBF) was examined using a laser Doppler flowmeter in anesthetized rats. One or two acupuncture needles were inserted into the skin and underlying muscles at a depth of about 5 mm. One needle was manually twisted to the right and left once a second for 1 min and two needles were used to pass an electrical current. Stimulation of the forepaw produced increases in CBF and mean arterial pressure (MAP) in spinal cord-intact rats. After spinal transection at the first to second thoracic level, the blood pressure response to manual or electrical stimulation of the forepaw was suppressed, whereas an increase in CBF still occurred. The increase in CBF induced by forepaw stimulation was abolished by severing the somatic nerves at the brachial plexus. Forepaw stimulation enhanced the activity of the radial, ulnar, and median nerves. An increase in CBF was elicited by excitation of group III (Aδ) and group IV (C) somatic afferent fibers. The CBF response was almost abolished by the i.v. administration of muscarinic and nicotinic cholinergic blocking agents (atropine 5 mg/kg and mecamylamine 20 mg/kg), and by bilateral lesions in the nucleus basalis of Meynert. Acupuncture-like stimulation of a forepaw increased acetylcholine release in the cerebral cortex. We concluded that the increase in CBF, independent of systemic blood pressure, elicited by acupuncture-like stimulation is a reflex response in which the afferent nerve pathway is composed of somatic groups III and IV afferent nerves, and the efferent nerve pathway includes intrinsic cholinergic vasodilators originating in the nucleus basalis of Meynert.