AMG-900 The influence of the stimulus period was

The influence of the stimulus period was examined [9]. Acupuncture stimuli were applied for 15 minutes or 60 minutes at 1 Hz and 3–5 V to the Zusanli acupoint under anesthesia. Stimulation of the Zusanli acupoint increased blood fluidity (decreased the blood-flow time). Blood samples were collected from the abdominal vein after the applications of stimuli and were preprocessed with an anticoagulant (sodium heparin). The control group was anesthetized in the same manner as the experimental groups, but it was not subjected to stimulation. Both stimulation times, 15 minutes and 60 minutes, resulted in similar effects. Even with a short stimulation time, blood fluidity was enhanced, suggesting an immediate effect of acupuncture stimulation on blood fluidity.
These experimental reactions had immediate effects, which is in contrast with those of the acupuncture reactions reported previously: acupuncture analgesia through endogenic opioids and immune reactions caused by the application of an acupuncture stimulus [24]. The ability to control blood fluidity by using acupuncture showed that the acupuncture signal initiated at the acupoints was transferred to the AMG-900 through the afferent nervous pathway; therefore, it modulated the function of neurotransmitter systems such as the cardiovascular center. Output signaling cascades may improve blood fluidity through efferent neural regulation, such as that by the sympathetic nervous system [25].
The influence of the stimulation frequency was investigated [9]. Acupuncture stimuli were applied for 60 minutes at 1 Hz or 100 Hz at 3–5 V at the Zusanli acupoint under anesthesia. When the acupuncture stimulation frequency was changed, blood fluidity was enhanced at both 1 Hz and 100 Hz. This result indicated that blood fluidity was not affected by a change in the frequency of the stimulus.
A low-frequency (1–5 Hz) or a high-frequency (>100 Hz) stimulus is known to influence mechanisms other than those of acupuncture analgesia [26]. When the acupuncture analgesic systems are activated, even surgery can be performed under acupuncture anesthesia alone. A decrease in nociception might affect blood fluidity. Electric acupuncture stimuli of low frequency (l–5 Hz) cause the secretion of arterenol, serotonin, and β-endorphin in the central nervous system. In other words, secretion of these transmitters has analgesic and sedative effects on the descending pain modulatory system or the endogenic opioid system [26,27]. In addition, spinal segment-related analgesia occurs when high-frequency (>100 Hz) electric acupuncture is used. Gate control theory is thought to apply because this system does not compete with naloxone administration [27].
In the second set of experiments, the mechanism of action of acupuncture with the administration of medicine was investigated. The influence of naloxone, an antagonist of endogenous opioids, was investigated [9]. In the experimental group, the Zusanli acupoint was stimulated for 60 minutes while injecting naloxone [5 mg/kg, intraperitoneal (i.p.)] into the abdominal cavity every 10 minutes. Neither acupuncture stimulus nor naloxone was administered to the control group. Physiological saline was injected into the abdominal cavity every 10 minutes in the control group and in the group receiving only acupuncture without naloxone. The results showed that blood flow time decreased significantly in the Zusanli-stimulated and the Zusanli-stimulated plus naloxone groups, although the differences between these two groups were not statistically significant.
When it is considered that blood fluidity was not affected by a difference in stimulus frequency or naloxone administration, it can be surmised that the endogenic opioid system and the spinal segment system do not contribute to blood fluidity. It was speculated that acupuncture stimuli change blood fluidity through the automatic nervous system and axon reflexes and do not influence the opioid system and the spinal segment analgesic system [28].