Analgesic and physiological effect of electroacupuncture combined with epidural lidocaine in goats.

OBJECTIVE: To investigate physiological and antinociceptive effects of electroacupuncture (EA) with lidocaine epidural nerve block in goats. STUDY DESIGN: Prospective experimental trial. ANIMALS: Forty-eight hybrid male goats weighing 27 ± 2 kg. METHODS: The goats were randomly assigned to six groups: L2.2, epidural lidocaine (2.2 mg kg-1); L4.4, epidural lidocaine (4.4 mg kg-1); EA; EA-L1.1, EA with epidural lidocaine (1.1 mg kg-1); EA-L2.2, EA with epidural lidocaine (2.2 mg kg-1); and EA-L4.4, EA with epidural lidocaine (4.4 mg kg-1). EA was administered for 120 minutes. Epidural lidocaine was administered 25 minutes after EA started. Nociceptive thresholds of flank and thigh regions, abdominal muscle tone, mean arterial pressure (MAP), heart rate (HR), respiratory frequency (fR) and rectal temperature were recorded at 30, 60, 90, 120, 150 and 180 minutes. RESULTS: Lidocaine dose-dependently increased nociceptive thresholds. There were no differences in nociceptive thresholds between L4.4 and EA from 30 to 120 minutes. The threshold in EA-L2.2 was lower than in EA-L4.4 from 30 to 120 minutes, but higher than in EA-L1.1 from 30 to 150 minutes or in L4.4 from 30 to 180 minutes. The abdominal muscle tone in EA-L2.2 was higher at 30 minutes, but lower at 90 and 120 minutes than at 0 minutes. There were no differences in muscle tone between L4.4 and L2.2 or EA-L4.4, and between any two of the three EA-lidocaine groups from 0 to 180 minutes. The fR and HR decreased in L4.4 at 60 and 90 minutes compared with 0 minutes. No differences in fR, HR, MAP and temperature among the groups occurred from 30 to 180 minutes. CONCLUSIONS AND CLINICAL RELEVANCE: EA combined with 2.2 mg kg-1 epidural lidocaine provides better antinociceptive effect than 4.4 mg kg-1 epidural lidocaine alone in goats. EA provided antinociception and allowed a decrease in epidural lidocaine dose.

Electroacupuncture relieves neuropathic pain via upregulation of glutamate transporters in the spinal cord of rats.

Glutamate transports (GTs), the only vehicle for removal of glutamate from the extracellular fluid, is reported to be related to chronic pain. To investigate whether the glutamate/aspartate transporter (GLAST) and glutamate transporter-1 (GLT-1) participate in electroacupuncture (EA) analgesia, the EA effect was observed with paw withdraw threshold in a rat model of spared nerve injury. The expression levels of GLAST and GLT-1 were determined with Western Blot and RT-PCR. The results showed significantly upregulated GLAST and GLT-1, along with the relieved pain behaviors after EA treatment. In addition, intrathecal injection of GTs inhibitor, l-trans-pyrrolidine-2-4-dicarboxylate, attenuated the EA-induced analgesic effect. The experiment demonstrates that EA can increase the GTs of neuropathic pain rats, which might be one of the mechanisms underlying its effectiveness in the neuropathic pain.

[Progress of Researches on Central Mechanism of Electroacupuncture Tolerance].

Electroacupuncture (EA) has been demonstrated effective for pain relief. However, repeated application may decline analgesic effect of EA, which is termed EA tolerance, that reduces the clinical efficacy of EA. Therefore, it has attracted attention from researchers in recent years and the progresses include:(1) acute and chronic EA tolerance animal models have been established; (2) cross-tolerance between EA and morphine; (3) Anti-opioid substances, including cholecystokinin, orphanin FQ and angiotensin Ⅱ, have been reported to contribute to EA tolerance; (4) glutamate receptors and transporters, 5-hydroxytryptamine and norepinephrine have been revealed involvement in EA tolerance; (5) cyclic adenosine monophosphate, cyclic guanosine monophosphate and Ca2+ have been reported to be the second messengers cellularly in EA tolerance. The current EA tolerance effect lacks in-depth researches. Therefore, studies on its molecular mechanisms and signaling pathway are necessarily required.

The Expression Patterns of c-Fos and c-Jun Induced by Different Frequencies of Electroacupuncture in the Brain.

To investigate patterns of c-Fos and c-Jun expression induced by different frequencies of electroacupuncture (EA) in the brain, goats were stimulated by EA of 0, 2, 60, or 100 Hz at a set of "Baihui, Santai, Ergen, and Sanyangluo" points for 30 min. The pain threshold was measured using the potassium iontophoresis method. The levels of c-Fos and c-Jun were determined with Streptavidin-Biotin Complex immunohistochemistry. The results showed that the pain threshold induced by 60 Hz was 82.2% higher (P < 0.01) than that by 0, 2, or 100 Hz (6.5%, 35.2%, or 40.9%). EA induced increased c-Fos and c-Jun expression in most analgesia-related nuclei and areas in the brain. Sixty Hz EA increased more c-Fos or c-Jun expression than 2 Hz or 100 Hz EA in all the measured nuclei and areas except for the nucleus accumbens, the area septalis lateralis, the caudate nucleus, the nucleus amygdala basalis, and the locus coeruleus, in which c-Fos or c-Jun expressions induced by 60 Hz EA did not differ from those by 2 Hz or 100 Hz EA. It was suggested that 60 Hz EA activated more extensive neural circuits in goats, which may contribute to optimal analgesic effects.