[Electroacupuncture improves insomnia by down-regulating peripheral benzodiazepine receptor expression in hippocampus, and up-regulating 5-HT, 5-HIAA, TNF-α and IL-1β contents in hypothalamus in insomnia rats]

Abstract

Objective: To observe the therapeutic effect of electroacupuncture (EA) at five Back-Shu points on sleep, hippocampal peripheral benzodiazepine receptor (PBR) expression and hypothalamic 5-hydroxytryptamine (5-HT), 5-hydroxyindoleacetic acid (5-HIAA), tumor necrosis factor alpha (TNF-α) and interleukin (IL)-1β contents in insomnia rats, so as to explore its mechanisms underlying improvement of insomnia.

Methods: Forty male SD rats were randomly divided into control, model, EA and medication (Diazepam) groups (n=10 rats in each group). The insomnia model was established by intraperitoneal injection (i.p.) of para-Chlorophenylalanine (PCPA, 300 mg/kg) once daily for 2 days. EA (60 Hz, 1 mA) was applied to bilateral five Back-Shu points, i.e., Feishu (BL13), Xinshu (BL15), Ganshu (BL18), Pishu (BL20) and Shenshu (BL23) for 10 min, once daily for 6 days. Rats of the medication group were treated by gavage of Diazepam (0.92 mg/kg) once daily for 6 days. The sleep duration was recorded after i.p. of Pentobarbital Sodium (45 mg/kg). Histopathological changes of the hippocampus were displayed by H.E. staining. The contents of 5-HT, 5-HIAA, TNF-α and IL-1β in the hypothalamus were assessed by using ELISA. The expression levels of PBR mRNA and protein in the hippocampus were detected by quantitative real-time PCR, immunohistochemistry and Western blot, separately.

Results: Following modeling, the sleep duration was considerably shortened in rats of the model group relevant to the control group (P<0.05). After the treatment, the sleep duration was significantly increased in both EA and medication groups relevant to the model group (P<0.05). After modeling, the hippocampal neurons were obviously decreased in number, and disordered in the arrangement, the levels of hypothalamic 5-HT, 5-HIAA, TNF-α, and IL-1β were significantly down-regulated (P<0.05), and the expression of PBR mRNA and protein in hippocampus was obviously increased relevant to the control group (P<0.05). Following the treatment, the hippocampal neurons were increased in number and arranged regularly, and the contents of hypothalamic 5-HT, 5-HIAA, TNF-α, and IL-1β were considerably increased (P<0.05), and the expression of PBR mRNA and protein in hippocampus was significantly decreased in both EA and medication groups relevant to the model group (P<0.05). The therapeutic effect of EA was comparable to that of medication in increasing sleep duration, body weight, 5-HT and 5-HIAA contents (P>0.05), and significantly superior to that of the medication in increasing TNF-α and IL-1β levels (P<0.05), and considerably superior to that of medication in down-regulating PBR mRNA and protein expression (P<0.05).

Conclusion: EA at five Back-Shu-points of the five Zang-organs can significantly improve the sleep in insomnia rats, which is closely associated with its effects in reducing the expression of PBR in hippocampus and up-regulating the levels of 5-HT, 5-HIAA, TNF-α and IL-1β in hypothalamus.

Keywords: Electroacupuncture; Five Back-Shu points; Insomnia; Peripheral benzodiazepine receptor.