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 F
B, F
D and F
W; and the membrane potentials were recorded as MP
B and MP
D. Picrotoxin (PTX) was used to block inhibitory gamma-aminobutyric acid type A (GABA
A) receptors during the application of propofol at 10 μmol·L
-1. Then, GABA
A 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 F
B, F
D and F
W during intralipid and 2 μmol·L
-1 propofol application. With propofol at 5, 10 and 20 μmol·L
-1, F
D decreased significantly when compared with F
B, and F
W increased significantly as compared with F
D (
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, MP
D 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 GABA
A receptors.