Propofol inhibits the local activity and connectivity of nuclei in the cortico-reticulo-thalamic loop in rats

Purpose The present study aimed to investigate the effects of different dosages of propofol, that induced different depths of anesthesia, on the local activity and connectivity of nuclei within the cortico-reticulo-thalamic loops, as well as the release of amino acids in those nuclei. Methods The nonlinear dynamics analysis of electroencephalogram, including approximate entropy (ApEn) and cross-ApEn (C-ApEn), was used to analyze the effects of different dosages of propofol on the local activity and connectivity of the important nuclei, including the primary somatosensory cortex (S1), ventroposteromedial thalamic nucleus (VPM), reticular thalamic nucleus (RTN), and oral part of the pontine reticular nucleus (PnO). The levels of glutamate (Glu), γ-aminobutyric acid (GABA), and glycine (Gly) in the S1, VPM, and RTN were detected using cerebral microdialysis. Results ApEn was more significantly reduced in the cortex than in the subcortical nuclei from awake to deep anesthesia state induced by propofol, and C-ApEn was also more significantly reduced between cortical nucleus and subcortical nucleus than between subcortical nuclei from awake to deep anesthesia state induced by propofol. Propofol inhibited the levels of Glu in S1 and VPM, but elevated the levels in RTN. Gly level decreased in S1, and GABA level increased in S1 after infusion of propofol. Conclusions The cortex rather than the subcortical structures, and the cortex–subcortical connectivity instead of subcortical connectivity might be the more vulnerable targets of propofol during anesthesia.