Acupuncture affects regional blood flow in various organs

Abstract

In this review, our recent studies using anesthetized animals concerning the neural mechanisms of vasodilative effect of acupuncture-like stimulation in various organs are briefly summarized. Responses of cortical cerebral blood flow and uterine blood flow are characterized as non-segmental and segmental reflexes. Among acupuncture-like stimuli delivered to five different segmental areas of the body; afferent inputs to the brain stem (face) and to the spinal cord at the cervical (forepaw), thoracic (chest or abdomen), lumbar (hindpaw) and sacral (perineum) levels, cortical cerebral blood flow was increased by stimuli to face, forepaw and hindpaw. The afferent pathway of the responses is composed of somatic groups III and IV afferent nerves and whose efferent nerve pathway includes intrinsic cholinergic vasodilators originating in the basal forebrain. Uterine blood flow was increased by cutaneous stimulation of the hindpaw and perineal area, with perineal predominance. The afferent pathway of the response is composed of somatic group II, III and IV afferent nerves and the efferent nerve pathway includes the pelvic parasympathetic cholinergic vasodilator nerves. Furthermore, we briefly summarize vasodilative regulation of skeletal muscle blood flow via a calcitonin gene-related peptide (CGRP) induced by antidromic activation of group IV somatic afferent nerves. These findings in healthy but anesthetized animals may be applicable to understanding the neural mechanisms improving blood flow in various organs following clinical acupuncture.

Keywords: axon reflex; cerebral blood flow; muscle blood flow; somato-autonomic reflex; uterine blood flow.

Figures

Figure 1.

The effect of acupuncture-like stimulation of various areas on CBF in the unilateral parietal cortex in central nervous system-intact rats. (A) Sample recordings of CBF in the parietal cortex ipsilateral to the stimulating site following acupuncture-like stimulation of the face, forepaw, chest, hindpaw and perineum for 1 min (indicated by horizontal bars). (B) Summary of CBF responses. Each point and vertical bar represent the mean ± SEM. *P < 0.05, **P < 0.01; significantly different from prestimulus control values using a paired t-test. Modified from Uchida et al. (19).

Figure 2.

(A) Diagram of the experiment demonstrating the microdialysis probe in the cortex. (B) Effects of acupuncture-like stimulation of the unilateral forepaw on extracellular ACh release in the parietal cortex ipsilateral to the stimulating site in central nervous system-intact rats. Each column and vertical bar show the mean ± SEM. **P < 0.01; significantly different from the prestimulus control value using one-way repeated ANOVA followed by Dunnett's multiple comparison test. (C–E) Effect of cholinergic receptor antagonist permeable to BBB on CBF response induced by electro-acupuncture stimulation of a forepaw in spinalized rats. ATR: atropine, 5 mg/kg, i.v. MEC: mecamylamine, 20 mg/kg, i.v. Modified from Uchida et al. (19).

Figure 3.

The effect of cutaneous stimulation of various areas on uterine blood flow in central nervous system-intact rats. (A and C) Sample recordings of uterine blood flow responses following pinching stimulation of various segmental areas of the body (A) or perineal brushing (C) for 1 min. (B) Summary of the responses of uterine blood flow to pinching of various skin areas and (D) brushing of the perineum. Changes in maximum responses of uterine blood flow during stimulation were calculated. Each column and vertical bar represent the mean ± SEM. *P < 0.05; **P < 0.01; significantly different from pre-stimulus control values, using t-test. Modified from Hotta et al. (23).

Figure 4.

Effects of cutaneous stimulation on uterine pelvic efferent nerve activity in central nervous system-intact rats. (A) Schematic diagram of experimental procedures for perineal stimulation and recording of uterine pelvic efferent nerve activity. (B) Sample recordings of uterine pelvic efferent nerve responses following perineal pinching. Modified from Hotta et al. (23).

Figure 5.

Schematic diagram of the reflex pathways for cerebral cortical and uterine blood vessels.

Figure 6.

The effect of antidromic stimulation of the unilateral dorsal roots (DR) of lumbar segments on ipsilateral MBF. (A) Schematic diagram of CGRP-related antidromic vasodilative action in muscles. (B) Sample recordings of blood flow of the biceps femoris muscle response to antidromic electrical stimulation of the L4 DR. Parameters of electrical stimulation are indicated. (C) The means and SEM of MBF responses to stimulation of L4-L5 DR before (closed circles) and after (open circles) topical application of hCGRP (8–37) (10−4 M). Changes in MBF were calculated every 30 s and are expressed as percentages of the pre-stimulus values just before stimulation (ordinate). The horizontal bar between the dashed vertical lines indicates the time during DR stimulation. Onset of electrical stimulation of DR is expressed as zero (abscissa). *P < 0.05; **P < 0.01; significantly different from pre-stimulus control values. Modified from Sato et al. (27).

Figure 7.

Schematic diagram showing neural mechanisms of blood flow responses in various organs induced by acupuncture and other somatic afferent stimulation.