Facial Stimulation Induces Long-Term Potentiation of Mossy Fiber-Granule Cell Synaptic Transmission via GluN2A-Containing N-Methyl-D-Aspartate Receptor/Nitric Oxide Cascade in the Mouse Cerebellum

Abstract

Long-term synaptic plasticity in the cerebellar cortex is a possible mechanism for motor learning. Previous studies have demonstrated the induction of mossy fiber-granule cell (MF-GrC) synaptic plasticity under in vitro and in vivo conditions, but the mechanisms underlying sensory stimulation-evoked long-term synaptic plasticity of MF-GrC in living animals are unclear. In this study, we investigated the mechanism of long-term potentiation (LTP) of MF-GrC synaptic transmission in the cerebellum induced by train of facial stimulation at 20 Hz in urethane-anesthetized mice using electrophysiological recording, immunohistochemistry techniques, and pharmacological methods. Blockade of GABAA receptor activity and repetitive facial stimulation at 20 Hz (240 pulses) induced an LTP of MF-GrC synapses in the mouse cerebellar cortical folium Crus II, accompanied with a decrease in paired-pulse ratio (N2/N1). The facial stimulation-induced MF-GrC LTP was abolished by either an N-methyl-D-aspartate (NMDA) receptor blocker, i.e., D-APV, or a specific GluNR2A subunit-containing NMDA receptor antagonist, PEAQX, but was not prevented by selective GluNR2B or GluNR2C/D subunit-containing NMDA receptor blockers. Application of GNE-0723, a selective and brain-penetrant-positive allosteric modulator of GluN2A subunit-containing NMDA receptors, produced an LTP of N1, accompanied with a decrease in N2/N1 ratio, and occluded the 20-Hz facial stimulation-induced MF-GrC LTP. Inhibition of nitric oxide synthesis (NOS) prevented the facial stimulation-induced MF-GrC LTP, while activation of NOS produced an LTP of N1, with a decrease in N2/N1 ratio, and occluded the 20-Hz facial stimulation-induced MF-GrC LTP. In addition, GluN2A-containing NMDA receptor immunoreactivity was observed in the mouse cerebellar granular layer. These results indicate that facial stimulation at 20 Hz induced LTP of MF-GrC synaptic transmission via the GluN2A-containing NMDA receptor/nitric oxide cascade in mice. The results suggest that the sensory stimulation-evoked LTP of MF-GrC synaptic transmission in the granular layer may play a critical role in cerebellar adaptation to native mossy fiber excitatory inputs and motor learning behavior in living animals.

Nicotine Facilitates Facial Stimulation-Evoked Mossy Fiber-Granule Cell Long-Term Potentiation in vivo in Mice

“…In addition, the normalized AUC of response was 131.2 ± 7.1% of baseline during 40-50 min after 20 Hz facial stimulation, which was similar to that of control (ACSF: 130.4 ± 7.7% of baseline; F = 0.27, P = 0.61; n = 8 experiments; Figure 3D), but significantly lower than that of nicotine alone (148.3 ± 7.5% of baseline; F = 9.85, P = 0.009; n = 8 experiments). These results indicated that blockade of α4β2 nAChRs abolished the nicotine-induced facilitation of facial Since facial stimulation at 20 Hz induced MF-GrC LTP in the mouse cerebellar granular layer through the NO cascade (Lu et al, 2022), we further examined whether nicotine enhances the facial stimulation-induced MF-GrC LTP via the NO signaling cascade. After perfusion of an NOS inhibitor, L-NNA (200 µM), on the cerebellar surface for 1 h, MF-GrC LTP could not be induced by delivery of 20 facial stimulation under the control condition (L-NNA) and in the presence of nicotine (NIC, 1 µM; L-NNA + NIC) (Figures 5A,B).…”

“…In the presence of picrotoxin (100 μM), air-puff (10 ms, 60 psi) of the ipsilateral whisker pad evoked a negative component in granular layer of mouse cerebellar cortical folium Crus II ( Figure 1A ). According to our previous studies ( Ma et al, 2019 ; Li et al, 2021 ; Lu et al, 2022 ), the facial stimulation-evoked response is identified as MF-GC synaptic transmission in the absence of GABAergic inhibitory inputs. For induction of long-term MF-GrC synaptic plasticity, 20 Hz air-puff stimulation (240 pulses) was delivered 10 min after facial stimulation-evoked response traces became stable ( Lu et al, 2022 ).…”

“…According to our previous studies (Ma et al, 2019;Li et al, 2021;Lu et al, 2022), the facial stimulation-evoked response is identified as MF-GC synaptic transmission in the absence of GABAergic inhibitory inputs. For induction of long-term MF-GrC synaptic plasticity, 20 Hz air-puff stimulation (240 pulses) was delivered 10 min after facial stimulation-evoked response traces became stable (Lu et al, 2022). (L-NNA), nitric oxide synthase (NOS) inhibitor, nicotine, methyllycaconitine citrate hydrate (MLA), and dihydroβ-erythroidine hydrobromide (DβEH) bought from Sigma-Aldrich (Shanghai, China).…”

“…The sensory information coming from MFs induces excitation of GrCs and long-term synaptic plasticity in the cerebellar granular layer ( Roggeri et al, 2008 ; D’Angelo and De Zeeuw, 2009 ). We recently found that 20 Hz facial stimulation produced LTP of MF-GrC synaptic transmission through an NMDA receptor/nitric oxide (NO) signaling pathway ( Lu et al, 2022 ). The sensory stimulation-induced long-term synaptic plasticity of MF-GrC synaptic transmission is assumed to play an important function during cerebellar adaptation to native MF excitatory inputs and motor learning behavior in living animals ( Roggeri et al, 2008 ; D’Angelo and De Zeeuw, 2009 ; Lu et al, 2022 ).…”

“…We recently found that 20 Hz facial stimulation produced LTP of MF-GrC synaptic transmission through an NMDA receptor/nitric oxide (NO) signaling pathway ( Lu et al, 2022 ). The sensory stimulation-induced long-term synaptic plasticity of MF-GrC synaptic transmission is assumed to play an important function during cerebellar adaptation to native MF excitatory inputs and motor learning behavior in living animals ( Roggeri et al, 2008 ; D’Angelo and De Zeeuw, 2009 ; Lu et al, 2022 ). In addition, activation of nAChRs facilitates glutamate release at the MF-GrC synapses in cerebellar slices ( De Filippi et al, 2001 ; Reno et al, 2004 ) and enhances facial stimulation-evoked MF-GrC synaptic transmission via activation of α7 and α4β2 nAChRs, which suggests that nicotine modulates sensory information-evoked MF-GrC long-term plasticity via nAChRs in vivo in mice ( Xu et al, 2019 ).…”