Alpha-adrenergic receptors in PVT neurons promote recovery from propofol anesthesia / 医学研究生学报

ABSTRACT

Objective The locus coeruleus noradrenergic system regulates the recovery process of general anesthesia, but its mechanism remains unclear. The locus coeruleus has a large amount of projection to the paraventricular nucleus of the thalamus (PVT). This study was to investigate the effect of the α-noradrenergic receptor in PVT neurons in propofol anesthesia. Methods The immunofluorescence technique was used for comparison of the c-fos expression in the PVT neurons collected from male SD rats under propofol anesthesia (the PA group, n = 4) or no anesthesia (the non-PA group, n = 4) and observation of the activity of PVT neurons. PVT microinjection models were established in 40 rats and randomized into four groups of equal number noradrenaline, phentolamine, propranolol, and isotonic saline. Under propofol anesthesia, the animals received microinjection of noradrenaline, phentolamine, propranolol, and isotonic saline at 1 μL into the PVT, respectively, and were observed for the time of recovery of righting reflex (RORR) and the δ (1-4 Hz), θ (4-8 Hz), α (8-12 Hz), β (12-25 Hz) and γ waves (25-60 Hz) on EEG before and after microinjection. Results The expression of c-fos was significantly reduced in the PA group compared with that in the non-PA control. The Ca2+ signals in the PVT were significantly increased during the propofol induction of the loss of righting reflex (LORR), but decreased in the early stage of and during propofol anesthesia (P < 0.05), and remarkably increased at the emergence of and during RORR (P < 0.05). In comparison with the isotonic saline control, the noradrenaline group showed markedly shortened time of RORR (837.8 s vs 647.7 s, P < 0.05), reduced rate of δ waves (P < 0.05) and elevated rate of β waves (P < 0.05), while the phentolamine group exhibited prolonged time of RORR (837.8 s vs 1045.1 s, P < 0.05) and increased rate of δ waves after microinjection (P < 0.05). Conclusion The α-noradrenergic receptors in PVT neurons play a critical role in promoting recovery from propofol anesthesia.