Effects of electroacupuncture on the somatosensory evoked response in rat

The Effect of Electro-Acupuncture on Spasticity of the Wrist Joint in Chronic Stroke Survivors

OBJECTIVE

To quantitatively assess the change in spasticity of the impaired wrist joint in chronic stroke patients after electro-acupuncture treatment.

DESIGN

Crossover design.

SETTING

University medical center research laboratory.

PARTICIPANTS

Seven chronic stroke subjects (age, 63.14+/-7.01y).

INTERVENTION

Participants received two 6-week treatment regimens: combined electro-acupuncture and strengthening twice a week, and strengthening twice a week only. Muscle strength and spasticity of the wrist joint were quantified by using the Biodex multijoint System 3 Pro. Electro-acupuncture was given through a commercial electro-acupuncture device.

MAIN OUTCOME MEASURES

Velocity sensitivity of averaged speed-dependent reflex torque (VASRT); segmented averaged speed-dependent reflex torque (SASRT); Modified Ashworth Scale (MAS) scores; and integrated electromyographic activity of the affected wrist flexors during passive stretch of the affected wrist joint.

RESULTS

VASRT was reduced significantly in the combined treatment group (P=.02) after the 6-week period, but not in the strengthening-only group (P=.23); however, no significant immediate effect of electro-acupuncture was observed (P>.05). MAS scores also showed a significant reduction (P<.01). SASRT did not differ significantly across different positions of the joint or across velocity; however, significant differences were present between the 2 treatment groups (P<.05) for each position and at all the velocities except at 20 degrees /s. Integrated electromyographic activity showed a trend for reduction after the combined treatment.

CONCLUSIONS

A combination of electro-acupuncture and muscle strengthening exercise for 6 weeks significantly reduced spasticity. The effect of spasticity reduction was consistent across different joint positions and different velocities of passive stretch.

Acupuncture decreases somatosensory evoked potential amplitudes to noxious stimuli in anesthetized volunteers

The effect of acupuncture on pain perception is controversial. Because late amplitudes of somatosensory evoked potentials (SEPs) to noxious stimuli are thought to correlate with the subjective experience of pain intensity, we designed this study to detect changes of these SEPs before and after acupuncture in a double-blinded fashion. Sixteen volunteers were anesthetized by propofol and exposed to painful electric stimuli to the right forefinger. Then, blinded to the research team, the acupuncture group (n = 8) was treated with electric needle acupuncture over 15 min at analgesic points of the leg, whereas the sham group (n = 8) received no treatment. Thereafter, nociceptive stimulation was repeated. SEPs were recorded during each noxious stimulation from the vertex Cz, and latencies and amplitudes of the N150 and P260 components were analyzed by analysis of variance. P260 amplitudes decreased from 4.40 +/- 2.76 microV (mean +/- SD) before treatment to 1.67 +/- 1.21 microV after treatment (P < 0.05), whereas amplitudes of the sham group remained unchanged (2.64 +/- 0.94 microV before versus 2.54 +/- 1.54 microV after treatment). In conclusion, this double-blinded study demonstrated that electric needle acupuncture, as compared with sham treatment, significantly decreased the magnitudes of late SEP amplitudes with electrical noxious stimulation in anesthetized subjects, suggesting a specific analgesic effect of acupuncture.

IMPLICATIONS

This double-blinded study demonstrates that electric needle acupuncture, as compared with sham treatment, significantly decreases the magnitudes of late somatosensory evoked potential amplitudes with electrical noxious stimulation in anesthetized subjects, suggesting a specific analgesic effect of acupuncture.

Early-latency somatosensory evoked potentials elicited by electrical acupuncture after needling acupoint LI-4

The stimulating methods of prior studies on somatosensory evoked potentials (SEPs) elicited by acupoint stimulus had involved surface electrodes, while the clinical practice of acupuncture is mostly performed by inserting the acupuncture needle inside the body. Clinical observations show that there are often some special sensations when LI-4 is needled. To observe if the SEPs produced by acupoint acupuncture had a distinguishing property, we studied the SEPs elicited by electrical acupuncture after the acupuncture needle was inserted into LI-4 and its control point, and then mapped them with the 128-channel Electric Brain Signal Image system. We also compared this to SEPs by median nerve stimuli. Results showed that the most interesting finding was the marked differences of N1-P1 and N2-P2 amplitude between SEPs at LI-4 (SEP-LI) and its control point (SEP-CP), which were in the opposite direction. Marked differences were also found between latencies and amplitudes of the SEPs elicited by acupuncture and by median nerve stimulus (SEP-M). The differences between SEP-LI and SEP-CP might be due to the additional effects of the activation of nerve endings and muscle spindles in LI-4 to the SEPs formed by the activation of superficial and deep radial nerves during electrical acupuncture. The differences between SEPs to acupoint and median nerve stimuli might be mainly due to the different distances from the stimulated regions to the cerebral cortex, the diversity and the number of activated fibers.

Response of raphe magnus neurons after acupuncture stimulation in rat

Extracellular recording was made from single cells in the nucleus raphe magnus (NRM) of Wistar albino rats. The spontaneous firing rate of these cells increased, decreased or was not altered after acupuncture stimulation. Excitatory response of the cells was obtained more often than the other ones. There were no significant differences between the effects induced by stimulation of meridian and nonmeridian points. It is suggested that only the excited neuron may participate directly in the descending analgesic system through NRM cells activated by acupuncture stimulation. Presumably, meridian point is not a specific one for activation of NRM cells in rat.

Inhibitory actions produced by local electrical stimulation in the caudal spinal trigeminal nucleus in rat

Inhibitory actions induced by local electrical stimulation (LES) on the tooth pulpal afferent activities were investigated in the caudal part of the rat spinal trigeminal nucleus. For the LES, ipsilateral Yin-Hsiang (intrasegmental point) or Ho-Ku (extrasegmental point) was used as a cathodal point which was stimulated electrically by a single pulse of 0.1 msec in duration or by 0.1 msec-pulse train at 45 Hz for 15 min. We found at least three types of inhibitions in the caudal trigeminal nucleus: Type I--this inhibition is the most forceful, caused by naloxone-reversible endogenous opiate system with a slow onset and prolonged aftereffect. This inhibition is presumably postsynaptic action. Type II--this is evoked by postsynaptical acting inhibition and begins within milliseconds after the stimulus is applied. Type III--this inhibition is elicited by presynaptic action and also begins within milliseconds after the onset of the stimulation. Type I and II inhibitions are evoked by stimulating either intra- or extrasegmental LES points, however, Type III is produced by stimulation of intrasegmental and rarely provoked by extrasegmental point stimulation. Naloxone failed to reverse Type II and III inhibitions. During LES, Type I to III inhibitions co-work for producing the suppressive effect and after the cessation of its stimulation, only Type I inhibition produces the so-called aftereffect of the LES.

Morphine and electroacupuncture: comparison of the effects on the cortical evoked responses after tooth pulp stimulation in rats

The effects of morphine and electroacupuncture on the cortical evoked responses after tooth pulp stimulation were investigated in rats. Morphine suppressed these responses more strongly in secondary somatosensory areas than those in primary somatosensory areas, while electroacupuncture suppressed the responses to the same degree in both areas. These results might suggest that there are some differences in noxious-suppressive action between morphine and the endogenous opiates released by electroacupuncture stimulation.