[Effect of acupuncture on neuronal function in the thalamic reticular nucleus of insomnia rats based on α7-nAChR]

To investigate the role of α7-nicotinic acetylcholine receptor (α7-nAChR) in the regulation of neuronal activity and expression of synapse-related proteins in the thalamic reticular nucleus (TRN) of insomnia rats treated by acupuncture.

A total of 36 male Sprague-Dawley (SD) rats of clean grade were randomly divided into a control group, a model group, an acupuncture group, and an acupuncture+antagonist group, with 9 rats in each group. The model group, the acupuncture group, and the acupuncture+antagonist group were treated with intraperitoneal injection of p-chlorophenylalanine (PCPA) to establish insomnia model. After successful modeling, the acupuncture group and the acupuncture+antagonist group received acupuncture at bilateral Neiguan (PC6) and Zusanli (ST36) once daily for 5 consecutive days. Thirty min before each acupuncture session, the acupuncture+antagonist group was intraperitoneally injected with methyllycaconitine citrate (MLA), an α7-nAChR antagonist, at a dosage of 5 mg/kg while the acupuncture group received the same volume of 0.9% sodium chloride solution. The rats' daytime spontaneous activity was observed. Neuronal discharge in the TRN was detected using neuroelectrophysiological methods. Immunofluorescence staining was used to detect parvalbumin-positive (PV⁺) neurons and co-expression of PV⁺ and postsynaptic density protein-95 (PSD-95) in the TRN.

Compared with the control group, the model group showed increased daytime spontaneous activity (P<0.01); decreased average fluorescence intensity and positive number of PV⁺ neurons in the TRN (P<0.01); decreased neuronal discharge frequency (P<0.01), prolonged inter-discharge intervals (P<0.01) in the TRN; reduced number of PV⁺/PSD-95 double-positive cells in the TRN (P<0.01). Compared with the model group, the acupuncture group showed decreased daytime spontaneous activity (P<0.01); increased average fluorescence intensity and positive number of PV⁺ neurons in the TRN (P<0.01); increased neuronal discharge frequency (P<0.01), shortened inter-discharge intervals (P<0.01) in the TRN; increased number of PV⁺/PSD-95 double-positive cells in the TRN (P<0.05). Compared with the acupuncture group, the acupuncture+antagonist group exhibited increased daytime spontaneous activity (P<0.01); reduced average fluorescence intensity and positive number of PV⁺ neurons in the TRN (P<0.01); decreased neuronal discharge frequency (P<0.05), prolonged inter-discharge intervals (P<0.05) in the TRN; reduced number of PV⁺/PSD-95 double-positive cells in the TRN (P<0.01).

α7-nAChR are involved in mediating the regulatory effect of acupuncture on circadian rhythm disturbances in PCPA-induced insomnia rats. Blocking α7-nAChR attenuates the activating effect of acupuncture on TRN neurons, and reduces the expression of PSD-95 protein on GABAergic neurons.