Eitaro Noguchi

The effect of electro-acupuncture stimulation on the muscle blood flow of the hindlimb in anesthetized rats.

The effect of electro-acupuncture stimulation (EAS) on blood flow in the muscle biceps femoris (MBF) and on mean arterial pressure (MAP) was investigated in anesthetized, artificially ventilated rats. EAS was applied to a hindpaw for 30 s at intensities of 0.1-10.0 mA and at frequencies of 1-20 Hz, and MBF was measured by laser Doppler flowmetry. EAS at less than 1.0 mA, which excited group II fibers maximally and III fibers partially in a saphenous nerve, had no significant effect on MBF or MAP, although both revealed variable responses. EAS at 1.5 mA, which additionally excited group III fibers almost maximally and was subthreshold for group IV fibers, produced a small but significant increase in MBF and MAP. These responses were further increased at 2.0 mA or more, which was suprathreshold for group IV fibers. The increased response of MBF at 10.0 mA was followed by a small decrease in MBF. EAS at 1.5 mA or more also elicited a decrease in renal blood flow (RBF) and an arterial pressor response. Following severance of the bilateral splanchnic nerves, EAS at 10.0 mA induced only a slight increase in MAP and a decrease in MBF. The decrease in MBF was abolished following further severance of the bilateral lumbar sympathetic trunks (LSTs). In conclusion, EAS to a hindpaw at a stimulus strength sufficient to excite group III and IV afferent fibers, particularly group IV afferent fibers, can produce a reflex decrease in MBF via a reflex activation of muscle sympathetic activity, although this decrease in MBF is overridden by an increase in MBF caused passively by a reflex MAP pressor response elicited by a reflex increase, at least in splanchnic sympathetic activity.

Electro-acupuncture stimulation to a hindpaw and a hind leg produces different reflex responses in sympathoadrenal medullary function in anesthetized rats.

The effects of electro-acupuncture stimulation (EAS) of two different areas of a hindlimb with different stimulus intensities on sympathoadrenal medullary functions were examined in anesthetized artificially ventilated rats. Two needles of 160 microm diameter and about 5 mm apart were inserted about 5 mm deep into a hindpaw (Chungyang, S42) or a hind leg (Tsusanli, S36) and current of various intensities passed to excite various afferent nerve fiber groups at a repetition rate of 20 Hz and pulse duration of 0.5 ms for 30-60 s. Fiber groups of afferent nerves stimulated in a hindlimb were monitored by recording evoked action potentials from the afferents innervating the areas stimulated. The sympathoadrenal medullary functions were monitored by recording adrenal sympathetic efferent nerve activity and secretion rates of catecholamines from the adrenal medulla. EAS of a hindpaw at a stimulus strength sufficient to excite the group III and IV somatic afferent fibers produced reflex increases in both adrenal sympathetic efferent nerve activity and the secretion rate of catecholamines. EAS of a hind leg at a stimulus strength sufficient to excite the group III and IV afferent fibers produced reflex responses of either increases or decreases in sympathoadrenal medullary functions. All responses of adrenal sympathetic efferent nerve activity were lost after cutting the afferent nerves ipsilateral to the stimulated areas, indicating that the responses are the reflexes whose afferents nerve pathway is composed of hindlimb somatic nerves. It is concluded that electro-acupuncture stimulation of a hindpaw causes an excitatory reflex, while that of a hind leg causes either excitatory or inhibitory reflex of sympathoadrenal medullary functions, even if both group III and IV somatic afferent fibers are stimulated.

Neural mechanism of localized changes in skeletal muscle blood flow caused by moxibustion-like thermal stimulation of anesthetized rats

Moxibustion-like thermal stimulation (MTS) was applied to the gastrocnemius muscle to measure local muscle blood flow (MBF) in the stimulated region and the change in the MBF in the region, and its mechanism was examined. In the experiment, we used urethane-anesthetized rats under artificial respiration and observed the change caused by gastrocnemius MTS using a laser Doppler blood-flow meter. MTS applied to the gastrocnemius muscle caused a two-phase response in blood flow that showed a transient decrease followed by an increase without blood pressure change. It is suggested that the increase in response occurs because of an axon reflex that has a reflex arc below the spinal cord, and the decrease in response is caused by direct stimulation of postganglionic muscle sympathetic fibers.

Body surface stimulation and rectal motility

Abstract The effects of mechanical stimulation on various skin areas on rectal motility were examined in anesthetized rats as a model of human. The rectal motility was measured by the balloon method at a position about 4–6 cm from the anus. Mechanical stimulation of the perineum induced a characteristic contraction of the rectum. Stimulation of the other skin areas did not produce any responses in the rectal motility. After the spinal transection at the 1st to 2nd cervical level, stimulation on the hindpaw and lower abdomen as well as the perineum induced the characteristic contraction of the rectum. These responses were abolished by severance of the pelvic nerves. After the severance of the sympathetic nerves innervating the rectum, the rectal motility increased its frequency, behind which the stimulation-induced responses were hidden and could not be observed. These results indicate that rectal motility was modulated by cutaneous mechanical stimulation through a segmental spinal reflex mechanism in anesthetized rats.