[Study on the mechanism of electroacupuncture of "Neiguan" (PC 6) in inhibiting ventricular arrhythmia induced by hypothalamic electrostimulation in the rabbit].

OBJECTIVE

To research whether opiate receptors in the hypothalamic arcuate nuclei (ARC) participate in the inhibitory effect of electroacupuncture (EA) of "Neiguan" (PC 6) on ventricular arrhythmia in the rabbit.

METHODS

This research consists of three parts. 1) Effect of electrolytic lesion of hypothalamic ARC on EA-induced suppression of heart ventricular extrasystole (HVE): HVE model was established by electric stimulation (0.4-0.8 mA, wave-duration 0.5 ms, 50 Hz, 5-10 s every 5 min) of hypothalamic midline region (R/L: 0.5-1.5 mm; H: -5 - -4.5 mm) in 4 rabbits. Electrolytic lesion (5 mA, 20 s) was induced by delivering a direct current to ARC region (A 1, L/R: 0.5 mm, H: -7 mm) through a stainless steel electrode (anode). EA (0.25 mA, 5 Hz, pulse-duration 0.5 ms) was applied to "Neiguan" (PC 6) for 3 min, 4 times altogether. (2) Effect of microinjection of morphine in ARC area on HVE: After inducing HVE, morphine (2 microg/microl) was injected into hypothalamic ARC region, and changes of HVE number were observed in 12 rabbits (6 for morphine group and the other 6 for normal saline group). (3) Effect of ARC microinjection of naloxone on EA-induced suppression of HVE: After inducing stable HVE, microinjection of naloxone (2 microg/microl) or same dose of normal saline was performed into ARC region in 6 rabbits respectively, followed by EA of PC6.

RESULTS

Electric stimulation of hypothalamic midline region could induce continuous HVE. After EA, it decreased significantly in the occurrence rate (P<0.01). Following ARC region lesion, the effect of EA in inhibiting HVE disappeared. After microinjection of morphine into ARC region, the occurrence rate of HVE reduced apparently (P<0.01), while after microinjection of naloxone, the inhibitory effect of EA vanished. No significant changes were found in the occurrence rate and the inhibitory rate of HVE after microinjection of naloxone or normal saline in the ARC region (P>0.05).

CONCLUSION

Hypothalamic ARC and it's opium receptors participate in the inhibitory effect of EA on hypothalamic midline region electro-stimulation-induced HVE in the rabbit.