Corticotrophin-Releasing Factor Modulates the Facial Stimulation-Evoked Molecular Layer Interneuron-Purkinje Cell Synaptic Transmission in vivo in Mice.

Wen-Yuan Wu,Hua Jin,De-Lai Qiu,Yang Liu,Hong-Wei Wang,Yu-Zi Li,Mao-Cheng Wu,Chun-Ping Chu

doi:10.3389/fncel.2020.563428

Abstract

Corticotropin-releasing factor (CRF) is an important neuromodulator in central nervous system that modulates neuronal activity via its receptors during stress responses. In cerebellar cortex, CRF modulates the simple spike (SS) firing activity of Purkinje cells (PCs) has been previously demonstrated, whereas the effect of CRF on the molecular layer interneuron (MLI)–PC synaptic transmission is still unknown. In this study, we examined the effect of CRF on the facial stimulation–evoked cerebellar cortical MLI-PC synaptic transmission in urethane-anesthetized mice by in vivo cell-attached recording, neurobiotin juxtacellular labeling, immunohistochemistry techniques, and pharmacological method. Cell-attached recordings from cerebellar PCs showed that air-puff stimulation of ipsilateral whisker pad evoked a sequence of tiny parallel fiber volley (N1) followed by MLI-PC synaptic transmission (P1). Microapplication of CRF in cerebellar cortical molecular layer induced increases in amplitude of P1 and pause of SS firing. The CRF decreases in amplitude of P1 waveform were in a dose-dependent manner with the EC50 of 241 nM. The effects of CRF on amplitude of P1 and pause of SS firing were abolished by either a non-selective CRF receptor antagonist, α-helical CRF-(9-14), or a selective CRF-R1 antagonist, BMS-763534 (BMS, 200 nM), but were not prevented by a selective CRF-R2 antagonist, antisauvagine-30 (200 nM). Notably, application CRF not only induced a significant increase in spontaneous spike firing rate, but also produced a significant increase in the number of the facial stimulation–evoked action potential in MLIs. The effect of CRF on the activity of MLIs was blocked by the selective CRF-R1 antagonist, and the MLIs expressed the CRF-R1 imunoreactivity. These results indicate that CRF increases excitability of MLIs via CRF-R1, resulting in an enhancement of the facial stimulation–evoked MLI-PC synaptic transmission in vivo in mice.

Highlights

Corticotropin-releasing factor (CRF) is synthesized and secreted in many regions of the central nervous system and is distributed in the hypothalamus, cerebral cortex, amygdala, cerebellum, and spinal cord (Palkovits et al, 1987; Barmack and Young, 1990; Luo et al, 1994; Tian and Bishop, 2003; Ezra-Nevo et al, 2018b)
Consistent with our previous studies (Chu et al, 2011; Bing et al, 2015), air-puff stimulation of ipsilateral whisker pad (10 ms; 60 psi) evoked a sequence of excitatory component (N1) and an inhibitory component (P1) followed by a pause of simple spike (SS) firing (Figures 1A,B); P1 was identified as molecular layer interneuron (MLI)-Purkinje cells (PCs) GABAergic synaptic transmission onto cerebellar PCs, whereas N1 was induced by parallel fiber volley (Chu et al, 2011, 2012; Supplementary Material)
These results indicate that molecular layer application of CRF induces a dose-dependent increase in the facial stimulation– evoked MLI-PC synaptic transmission but without change in parallel fiber excitatory inputs in vivo in mice

Summary

Introduction

Corticotropin-releasing factor (CRF) is synthesized and secreted in many regions of the central nervous system and is distributed in the hypothalamus, cerebral cortex, amygdala, cerebellum, and spinal cord (Palkovits et al, 1987; Barmack and Young, 1990; Luo et al, 1994; Tian and Bishop, 2003; Ezra-Nevo et al, 2018b). The labeling of CRF-R2 has been found in the molecular layer, such as parallel fibers and their terminals (Tian et al, 2006) Both CRF-R1 and CRF-R2 were expressed in climbing fibers of the adult rat cerebellum (Swinny et al, 2003). Physiological studies demonstrated CRF binding to CRF receptors, modulating neuronal spontaneous spike firing activity in cerebellar cortex (Fox and Gruol, 1993; Gunn et al, 2017; Prouty et al, 2017). The release of CRF from climbing fibers can be reliably induced by direct electrical or chemical stimulation of the inferior olive, as well as by stimulation of specific sensory afferents (Palkovits et al, 1987; Barmack and Young, 1990; Tian and Bishop, 2003), and the reduction in CRF levels of the inferior olive nucleus is sufficient to induce motor deficiency under challenging conditions, irrespective of basal locomotion or anxiety-like behavior (Ezra-Nevo et al, 2018b). CRFergic fibers project to granular layer as mossy fibers to regulate their synaptic transmission and plasticity (Chen et al, 2000; Refojo et al, 2011; Kuhne et al, 2012), and it acts as critical roles in regulating particular forms of cerebellar learning both at the cellular and behavioral levels, but without an effect on baseline motor skills (Ezra-Nevo et al, 2018a)

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