Study on after-effect of electroacupuncture with different time intervals on corticospinal excitability in primary motor cortex / 中国针灸

OBJECTIVES@#To compare the effects of electroacupuncture (EA) with different time intervals on corticospinal excitability of the primary motor cortex (M1) and the upper limb motor function in healthy subjects and observe the after-effect rule of acupuncture.@*METHODS@#Self-comparison before and after intervention design was adopted. Fifteen healthy subjects were included and all of them received three stages of trial observation, namely EA0 group (received one session of EA), EA6h group (received two sessions of EA within 1 day, with an interval of 6 h) and EA48h group (received two sessions of EA within 3 days, with an interval of 48 h). The washout period among stages was 1 week. In each group, the needles were inserted perpendicularly at Hegu (LI 4) on the left side, 23 mm in depth and at a non-acupoint, 0.5 cm nearby to the left side of Hegu (LI 4), separately. Han's acupoint nerve stimulator (HANS-200A) was attached to these two needles, with continuous wave and the frequency of 2 Hz. The stimulation intensity was exerted higher than the exercise threshold (local muscle twitching was visible, and pain was tolerable by healthy subjects, 1-2 mA ). The needles were retained for 30 min. Using the single pulse mode of transcranial magnetic stimulation (TMS) technique, before the first session of EA (T0) and at the moment (T1), in 2 h (T2) and 24 h (T3) after the end of the last session of EA, on the left first dorsal interosseous muscle, the amplitude, latency (LAT), resting motor threshold (rMT) of motor evoked potentials (MEPs) and the completion time of grooved pegboard test (GPT) were detected. Besides, in the EA6h group, TMS was adopted to detect the excitability of M1 (amplitude, LAT and rMT of MEPs) before the last session of EA (T0*).@*RESULTS@#The amplitude of MEPs at T1 and T2 in the EA0 group, at T0* in the EA6h group and at T1, T2 and T3 in the EA48h group was higher when compared with the value at T0 in each group separately (P<0.001). At T1, the amplitude of MEPs in the EA0 group and the EA48h group was higher than that in the EA6h group (P<0.001, P<0.01); at T2, it was higher in the EA0 group when compared with that in the EA6h group (P<0.01); at T3, the amplitude in the EA0 group and the EA6h group was lower than that of the EA48h group (P<0.001). The LAT at T1 was shorter than that at T0 in the three groups (P<0.05), and the changes were not obvious at the rest time points compared with that at T0 (P > 0.05). The GPT completion time of healthy subjects in the EA0 group and the EA48h group at T1, T2 and T3 was reduced in comparison with that at T0 (P<0.001). The completion time at T3 was shorter than that at T0 in the EA6h group (P<0.05); at T2, it was reduced in the EA48h group when compared with that of the EA6h group (P<0.05). There were no significant differences in rMT among the three groups and within each group (P>0.05).@*CONCLUSIONS@#Under physiological conditions, EA has obvious after-effect on corticospinal excitability and upper limb motor function. The short-term interval protocol (6 h) blocks the after-effect of EA to a certain extent, while the long-term interval protocol (48 h) prolongs the after-effect of EA.

Effect of electroacupuncture combined with motor training on motor learning and motor cortex excitability / 中国针灸

OBJECTIVE@#To compare the effect of electroacupuncture (EA), motor training (MT) and EA combined with MT on motor learning and motor cortex excitability in healthy subjects, and to explore the effect of EA combined with MT on synaptic metaplasticity.@*METHODS@#Using self-control design, 12 healthy subjects were assigned into an EA group, a motor training group (MT group) and an EA plus motor training group (EA+MT group) successively, wash-out period of at least 2 weeks was required between each group. EA was applied at left Hegu (LI 4) in the EA group for 30 min, with continuous wave, 2 Hz in frequency and 0.5-1 mA in density. Motor training of left hand was adopted in the MT group for 30 min. EA and motor training were adopted in the EA+MT group successively. The time of finishing grooved pegboard test (GPT) was observed, and the average amplitude of motor evoked potentials (MEPs), the rest motor threshold (rMT) and the latency were recorded by transcranial magnetic stimulation technique before intervention (T0), after intervention (T1) and 30 min after EA (T3) in the EA group and the EA+MT group, T0 and T1 in the MT group.@*RESULTS@#Compared with T0, the time of finishing GPT was shortened at T1 in the MT group and at T2 in the EA group and the EA+MT group (@*CONCLUSION@#In physiological state, electroacupuncture combined with motor training have a synergistic effect on motor learning, while have no such effect on excitability of cerebral motor cortex.

Enhancement of GluN2B Subunit-Containing NMDA Receptor Underlies Serotonergic Regulation of Long-Term Potentiation after Critical Period in the Rat Visual Cortex

Serotonin [5-hydroxytryptamine (5-HT)] regulates synaptic plasticity in the visual cortex. Although the effects of 5-HT on plasticity showed huge diversity depending on the ages of animals and species, it has been unclear how 5-HT can show such diverse effects. In the rat visual cortex, 5-HT suppressed long-term potentiation (LTP) at 5 weeks but enhanced LTP at 8 weeks. We speculated that this difference may originate from differential regulation of neurotransmission by 5-HT between the age groups. Thus, we investigated the effects of 5-HT on apha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR)-, gamma-aminobutyric acid receptor type A (GABA(A)R)-, and N-methyl-D-aspartic acid receptor (NMDAR)-mediated neurotransmissions and their involvement in the differential regulation of plasticity between 5 and 8 weeks. AMPAR-mediated currents were not affected by 5-HT at both 5 and 8 weeks. GABA(A)R-mediated currents were enhanced by 5-HT at both age groups. However, 5-HT enhanced NMDAR-mediated currents only at 8 weeks. The enhancement of NMDAR-mediated currents appeared to be mediated by the enhanced function of GluN2B subunit-containing NMDAR. The enhanced GABA(A)R- and NMDAR-mediated neurotransmissions were responsible for the suppression of LTP at 5 weeks and the facilitation of LTP at 8 weeks, respectively. These results indicate that the effects of 5-HT on neurotransmission change with development, and the changes may underlie the differential regulation of synaptic plasticity between different age groups. Thus, the developmental changes in 5-HT function should be carefully considered while investigating the 5-HT-mediated metaplastic control of the cortical network.

The Concept of Metaplasticity

The concept of metaplasticity entails a change in the physiological or biochemical state of synapses that alters their ability to generate synaptic plasticity by integrating individual synaptic events. The characteristics of metaplasticity would be the fact that those synaptic changes last in certain period time with association of activity in time, homosynaptically or heterosynaptically. Recently introduced non-invasive brain stimulation enables us to observe the metaplastic changes in vivo, which would give us a insight in developing new effective therapeutic approach based on synaptic plasticity and metaplasticity.