Midazolam Exerts Sedative Effects by Differentially Modulating Cortical Pyramidal Neurons and PV Interneurons.

AIMS: Midazolam is a sedative that acts on γ-aminobutyric acid type A receptors, but whether its effects are region-specific, especially in the neocortex, and the mechanisms underlying these effects remain unclear.

METHODS

Using microendoscopic Ca2+ imaging and whole-cell recording in brain slices, we systematically investigated the effects of midazolam on excitatory pyramidal neurons and inhibitory parvalbumin-positive interneurons (PV+) in the mouse auditory cortex (AC) and anterior cingulate cortex (ACC).

RESULTS

Midazolam dose-dependently suppressed pyramidal neurons more potently in the AC than in the ACC (Evoked: pyramidal neurons: 0.65 ± 0.30 vs. 1.36 ± 0.34, p < 0.0001; Spontaneous: pyramidal neurons: 1.49 ± 0.48 vs. 2.25 ± 0.42, p = 0.0006). In slices, midazolam reduced the action potential firing of pyramidal neurons in a concentration-dependent manner, with greater sensitivity in the AC. In contrast, PV+ neurons showed little change in intrinsic excitability in either region. Functional assays suggested that midazolam responsiveness was associated with GABRA1 expression, which was higher in AC pyramidal neurons than in those of the ACC (1.77 ± 0.55 vs. 1.01 ± 0.36, p = 0.002), while PV+ neurons showed no significant regional difference in GABRA1 expression.

CONCLUSION

Midazolam suppresses cortical excitatory neurons in a region- and cell-type-dependent manner that is associated with differential expression of GABRA1.