ABSTRACT
This study explored the effects of propofol on the activity of glutamatergic neurons in the paraventricular thalamus (PVT) and the underlying mechanisms at the molecular level using whole-cell patch-clamp techniques. Acute brain slices containing the PVT were obtained from 8 weeks old C57BL/6J mice. The electrophysiological characteristics of PVT neurons were recorded in current-clamp mode, then single-cell sequencing was used to identify neuronal types. The firing frequencies before, during, and after propofol or intralipid application were recorded as FB, FD and FW; and the membrane potentials were recorded as MPB and MPD. Picrotoxin (PTX) was used to block inhibitory gamma-aminobutyric acid type A (GABAA) receptors during the application of propofol at 10 μmol·L-1. Then, GABAA receptor-mediated spontaneous and miniature inhibitory postsynaptic currents (sIPSCs and mIPSCs) were recorded, and the effects of 10 μmol·L-1 propofol were investigated. The animal experiments were approved by the Medical Animal Administrative Committee of Shanghai Medical College Fudan University. The results showed that there were no significant differences in FB, FD and FW during intralipid and 2 μmol·L-1 propofol application. With propofol at 5, 10 and 20 μmol·L-1, FD decreased significantly when compared with FB, and FW increased significantly as compared with FD (P < 0.01). The inhibition degree of the three concentration groups was significantly different (P < 0.01). In addition, with propofol at 20 μmol·L-1, MPD hyperpolarized significantly (P < 0.01). In the presence of PTX, 10 μmol·L-1 propofol could not suppress the firing frequency of PVT glutamatergic neurons. Propofol at 10 μmol·L-1 prolonged the decay time of sIPSCs (P < 0.01) and mIPSCs (P < 0.05), and increased the amplitude (P < 0.01) of mIPSCs of PVT glutamatergic neurons. Together, these results indicate that propofol can inhibit the activity of PVT glutamatergic neurons in a concentration-dependent and reversible manner, and the effect is likely to be mediated by postsynaptic GABAA receptors.
ABSTRACT
Objective:To investigate the effect of ginkgo biloba extract (GBE) on oxidative stress in medial prefrontal cortex and excitatory/inhibitory balance of pyramidal neurons in chronic unpredictable mild stress (CUMS)-induced depressive model mice.Methods:Totally 48 SPF grade 7-week-old male C57BL/6J mice were divided into 4 groups according to random number table method: control+ saline group (CTRL+ Veh), control+ GBE group (CTRL+ GBE), model+ saline group (CUMS+ Veh), model+ GBE group (CUMS+ GBE), with 12 mice in each group.Mice in CUMS+ Veh group and CUMS+ GBE group were established by CUMS method, and mice in CTRL+ GBE group and CUMS+ GBE group were intraperitoneally injected with GBE (70 mg/kg) once a day, and mice in CTRL+ Veh group and CUMS+ Veh group were injected intraperitoneally with 0.9% sodium chloride solution.Then, the sucrose preference test, forced swimming test (FST) and tail suspension test (TST) were performed to evaluate the depressive-like behavior of mice, and open field test (OFT) was performed to evaluate the autonomous locomotion and exploration ability and anxiety-like behavior.The content of malondialdehyde (MDA) and activity of superoxide dismutase (SOD) in mPFC were determined by ELISA.Spontaneous excitatory postsynaptic currents (sEPSC) and spontaneous inhibitory postsynaptic currents (sIPSC) were detected by whole-cell recording.SPSS 23.0 was used for data analysis and two-factor analysis of variance(whether to get GBE, whether to mold, show as GBE×CUMS) was used for statistical analysis.Results:(1) Behavioral results: the the time spent in center and total distance of OFT and sugar preference rate of the four groups of mice were compared, and the interaction of GBE×CUMS was significant( F=24.90, 4.82, 3.91, all P<0.05). The results of simple effect analysis showed that the time spent in center ((47.15±3.58) s), the total distance((19.33±0.86) m) and the sugar preference rate((59.11±8.79)%) of the mice in CUMS+ Veh group were lower than those in the CTRL+ Veh group((61.55±2.49) s, (23.24±1.21) m, (84.02±7.45) %) (all P<0.01), and the above indexes in CUMS+ GBE group ((56.51±3.53) s, (20.75±1.31) m, (70.80±11.79)%) were higher than those in CUMS+ Veh group (all P<0.05). In the immobility time of FST and TST of mice in the 4 groups, the interaction of GBE×CUMS were significant( F=85.53, 83.39, both P<0.01). The immobility time of FST and TST in CUMS+ Veh group were higher than those in CTRL+ Veh group (both P<0.01 ), and the above indexes in CUMS+ GBE group were lower than CUMS+ Veh group(both P<0.05). (2)The results of ELISA showed that the interaction of GBE×CUMS of SOD level of mice in the 4 groups was not significant ( F=3.52, P=0.07), but the main effects of GBE factor and CUMS factor were both significant ( F=4.69, 46.93, both P<0.05). The interaction of GBE×CUMS of MDA level was significant( F=16.61, P<0.01). The level of SOD in the CUMS+ Veh group was lower than that in the CTRL+ Veh group ( P<0.01), and the level of SOD in the CUMS+ GBE group was higher than that in the CUMS+ Veh group ( P<0.05). The level of MDA in the CUMS+ Veh group was higher than that of the CTRL+ Veh group ( P<0.01), and the level of MDA in CUMS+ GBE group was lower than that of the CUMS+ Veh group ( P<0.01). (3) The results of whole-cell recording showed that the interaction of GBE×CUMS of frequency and quantification of sEPSC in the four groups were significant ( F=5.45, 6.94, both P<0.05). The sEPSC frequency and quantification in the CUMS+ Veh group were lower than those in the CTRL+ Veh group (both P<0.01), and the sEPSC frequency and quantification in CUMS+ GBE group were higher than those of CUMS+ Veh group (both P<0.05). The interaction of GBE×CUMS of frequency and quantification of sIPSC in the four groups were significant ( F=7.78, 8.96, both P<0.01). The sIPSC frequency and quantification of the CUMS+ Veh group were higher than those of CTRL+ Veh group (both P<0.01), and the above indexes of CUMS+ GBE group were lower than those of CUMS+ Veh group (both P<0.01). As for the sEPSC/sIPSC ratio, GBE×CUMS interaction was significant ( F=5.45, P=0.02). The sEPSC/sIPSC ratio of CUMS+ Veh group (0.09±0.01) was lower than that of CTRL+ Veh group (0.28±0.04) ( P<0.01), and the sEPSC/sIPSC ratio of CUMS+ GBE group (0.14±0.03) was higher than that of CUMS+ Veh group ( P<0.05). Conclusion:Ginkgo biloba extract can improve the depression-like behavior of mice induced by CUMS, reduce the oxidative stress of mPFC and improve the excitation/inhibition balance of pyramidal neurons in depressive model mice.
ABSTRACT
The hypothalamic paraventricular nucleus (PVN) contains two types of neurons projecting to either the rostral ventrolateral medulla (PVN(RVLM)) or the intermediolateral horn (IML) of the spinal cord (PVN(IML)). These two neuron groups are intermingled in the same subdivisions of the PVN and differentially regulate sympathetic outflow. However, electrophysiological evidence supporting such functional differences is largely lacking. Herein, we compared the electrophysiological properties of these neurons by using patch-clamp and retrograde-tracing techniques. Most neurons (>70%) in both groups spontaneously fired in the cell-attached mode. When compared to the PVN(IML) neurons, the PVN(RVLM) neurons had a lower firing rate and a more irregular firing pattern (p < 0.05). The PVN(RVLM) neurons showed smaller resting membrane potential, slower rise and decay times, and greater duration of spontaneous action potentials (p < 0.05). The PVN(RVLM) neurons received greater inhibitory synaptic inputs (frequency, p < 0.05) with a shorter rise time (p < 0.05). Taken together, the results indicate that the two pre-sympathetic neurons differ in their intrinsic and extrinsic electrophysiological properties, which may explain the lower firing activity of the PVN(RVLM) neurons. The greater inhibitory synaptic inputs to the PVN(RVLM) neurons also imply that these neurons have more integrative roles in regulation of sympathetic activity.
Subject(s)
Animals , Action Potentials , Fires , Horns , Inhibitory Postsynaptic Potentials , Membrane Potentials , Neurons , Paraventricular Hypothalamic Nucleus , Patch-Clamp Techniques , Spinal Cord , Spinal Cord Lateral HornABSTRACT
The medial vestibular nucleus (MVN) neurons are controlled by excitatory synaptic transmission from the vestibular afferent and commissural projections, and by inhibitory transmission from interneurons. Spontaneous synaptic currents of MVN neurons were studied using whole cell patch clamp recording in slices prepared from 13- to 17-day-old rats. The spontaneous inhibitory postsynaptic currents (sIPSCs) were significantly reduced by the GABAA antagonist bicuculline (20micrometer), but were not affected by the glycine antagonist strychnine (1micrometer). The frequency, amplitude, and decay time constant of sIPSCs were 4.3 0.9 Hz, 18.1 2.0 pA, and 8.9 0.4 ms, respectively. Spontaneous excitatory postsynaptic currents (sEPSCs) were mediated by non-NMDA and NMDA receptors. The specific AMPA receptor antagonist GYKI-52466 (50micrometer) completely blocked the non-NMDA mediated sEPSCs, indicating that they are mediated by an AMPA-preferring receptor. The AMPA mediated sEPSCs were characterized by low frequency (1.5 0.4 Hz), small amplitude (13.9 1.9 pA), and rapid decay kinetics (2.8 0.2 ms). The majority (15/21) displayed linear I-V relationships, suggesting the presence of GluR2-containing AMPA receptors. Only 35% of recorded MVN neurons showed NMDA mediated currents, which were characterized by small amplitude and low frequency. These results suggest that the MVN neurons receive excitatory inputs mediated by AMPA, but not kainate, and NMDA receptors, and inhibitory transmission mediated by GABAA receptors in neonatal rats.