Effects of different frequencies of electroacupuncture stimulation on the electroencephalogram and intracranial levels of prostaglandin D 2 and adenosine in rats under propofol anesthesia

Objective: To investigate the effects of different frequencies of electroacupuncture (EA) stimulation on the electroencephalogram (EEG) and intracranial levels of adenosine (Ad) and prostaglandin D 2 (PGD 2 ) in rats anesthetized using propofol. Methods: Thirty-six rats were divided into the manual acupuncture (MA), high-frequency EA (HF-EA) and low-frequency EA (LF-EA) groups (n = 12/group). After intravenous anesthesia with propofol, an EEG was recorded before and after stimulation at bilateral ST36 and PC6 using 50-Hz stimulation (HF-EA group) or 2/15-Hz stimulation (LF-EA group) versus no electrical stimulation (MA group). The brains were collected after the experiment to determine cortical and subcortical Ad and PGD 2 levels. The ventrolateral preoptic nucleus (VLPO) was collected for Ad immunohistochemistry. Results: There were changes in the δ wave in the LF-EA group and in the α, β and θ waves in the HF-EA group. Compared with the MA group, subcortical Ad levels were higher in the LF-EA group (0.96 ± 0.035 vs 0.93 ± 0.034 pmol/mL, p < 0.05). Cortical PGD 2 levels were higher in the LF-EA group than in the MA group (13.49 ± 0.440 vs 12.95 ± 0.436 pmol/mL, p < 0.05). VLPO Ad levels were significantly increased in the LF-EA group compared to both the HF-EA group (0.210 ± 0.0066 vs 0.201 ± 0.0065, p < 0.05) and the MA group (0.210 ± 0.0066 vs 0.199 ± 0.0095, p < 0.01). Conclusion: LF-EA at bilateral ST36 and PC6 may increase the depth of anesthesia and sedation, possibly through increased intracranial PGD 2 and Ad levels. However, such an effect was not found with HF-EA.