Spatiotemporal terahertz modulation enhances NMDAR-mediated miniature EPSCs

Abstract

N-Methyl-D-aspartate receptors (NMDAR) are essential for synaptic plasticity and cognitive function, making their modulation a promising strategy for treating disorders like schizophrenia and cognitive impairment. However, methods to selectively modulate NMDAR activity in the lesion's nucleus of the central nervous system remain limited. In this study, using whole-cell patch-clamp recordings, we demonstrated that frequency-specific (42.5 THz) terahertz irradiation significantly enhanced both the frequency and amplitude of NMDAR-mediated miniature excitatory postsynaptic currents (mEPSCs), a response closely linked to Ca²⁺ currents. The mechanism is elucidated via molecular dynamics (MD) simulations, revealing that 42.5 THz irradiation effectively alters the free energy landscape of Ca²⁺ permeating through the NMDAR channel. Specifically, THz photons resonated with key carboxyl groups at the Ca²⁺ binding site, leading to an increase in Ca²⁺ permeability and consequently enhanced mEPSCs. These findings suggest a novel physical therapy approach for treating cognitive deficits and neurological disorders associated with impaired NMDAR function.

Keywords: Molecular dynamics; NMDA receptors; Physical therapy; Terahertz photon; mEPSCs.

Fig. 1

Exposure to 42.5 THz photons significantly enhanced both the frequency and amplitude of NMDAR-mediated mEPSCs in neurons. (A) Schematic of THz irradiation on NMDA receptors. During THz exposure, AMPA receptors on the cell membrane were blocked using the specific antagonist CNQX, and extracellular Mg²⁺ was removed to enhance the NMDA currents. (B) Representative traces of NMDAR-mediated mEPSCs before (black curve) and during (orange curve) exposure to 42.5 THz irradiation (cell = 8). (C) Left panel: Frequency of NMDAR-mediated mEPSCs before and during 42.5 THz irradiation. Paired sample Wilcoxon signed-rank test, * p < 0.05. Right panel: Cumulative probability curve of the inter-event intervals of NMDAR-mediated mEPSCs before and during 42.5 THz irradiation. K–S test, p = 0.2827. (D) Left panel: Amplitude of NMDAR-mediated mEPSCs. Paired sample Wilcoxon signed-rank test, ** p < 0.01. Right panel: cumulative probability curve of the amplitude of NMDAR-mediated mEPSCs. K–S test, p = 0.2827. (E) Representative traces of NMDA-mediated mEPSCs before (black curve) and during (blue curve) 34.5 THz irradiation (cell = 8). (F) Left panel: frequency of NMDA-mediated mEPSCs before and during 34.5 THz irradiation. Paired sample Wilcoxon signed-rank test, p = 0.2500, where ns denotes no significant difference. Right panel: cumulative probability curve of the inter-event intervals of NMDA-mediated mEPSCs before and during 34.5 THz irradiation. K–S test, p = 0.9801. (G) Left panel: Amplitude of NMDA-mediated mEPSCs. Paired sample Wilcoxon signed-rank test, p = 0.1484. Right panel: Cumulative probability curve of the amplitude of NMDA-mediated mEPSCs. K–S test, p = 0.9801. (H) Left panel: The temperature sensor monitored temperature changes caused by THz irradiation at a distance of 300 μm from the optical fiber surface. Right panel: The temperature growth induced by 42.5 and 34.5 THz irradiation (n = 5). Mann-Whitney U-test, p = 0.8413.

Fig. 2

Exposure to 42.5 THz photons enhanced the amplitude of NMDA-mediated mEPSCs in neurons by increasing Ca²⁺ permeability. (A) NMDA receptors were blocked using the NMDA receptor antagonist AP5, while THz irradiation was simultaneously applied to the cells. (B) AP5 completely inhibited NMDAR-mediated mEPSCs (black curve), even in the presence of 42.5 THz irradiation (orange curve) (cell = 8). (C) Schematic representation indicating the removal of Ca²⁺ from the ACSF. (D) Representative trace of NMDAR-mediated mEPSCs in Ca²⁺ free ACSF before (black curve) and during (orange curve) the exposure to 42.5 THz irradiation (cell = 7). (E) Left panel: Frequency of NMDAR-mediated mEPSCs before and during 34.5 THz irradiation. Paired sample Wilcoxon signed-rank test, p = 0.2500, indicating no significant difference. Right panel: Cumulative probability curve of the inter-event intervals of NMDAR-mediated mEPSCs before and during 34.5 THz irradiation. K–S test, p = 0.5752. (F) Left panel: Amplitude of NMDAR-mediated mEPSCs. Paired sample Wilcoxon signed-rank test, p = 0.6250, denoting no significant difference. Right panel: Cumulative probability curve of the amplitude of NMDAR-mediated mEPSCs. K–S test, p = 0.9627.

Fig. 3

Mechanism underlying 42.5 THz irradiation modulating NMDA-mediated mEPSCs. (A) Left panel: schematic of Ca²⁺ passing the NMDA receptor under THz irradiation (orange light). Right panel: magnified view of the boxed region in left panel, highlighting Ca²⁺ (blue ball) passing through the putative calcium binding site, composed of residues 679–684 (pink chain). (B) Vibration spectra of bulk water (gray curve) and side chains of binding residues (orange curve for the carboxyl groups of Asp and Glu; green curve for the guanidinium group of Arg). (C-E) Heat maps of the free energy profiles under conditions without external irradiation (C) and with irradiations at 42.5 THz (D), 34.5 THz (E). (F-H) The number of hydrogen bonds between hydrated Ca²⁺ and Asp679 (F), Glu682 (G) and Glu683 (H) at the binding site with irradiation at 42.5 THz.