Morphological and electrophysiological properties of serotonin neurons with NMDA modulation in the mesencephalic locomotor region of neonatal ePet-EYFP mice

Serotonergic Modulation of Locomotor Activity From Basal Vertebrates to Mammals

“…Whether these reticulospinal neurons are 5-HT-positive is not known. Some Pet1-positive 5-HT neurons were recently described in the pedunculopontine nucleus, the ventral part of the MLR, but their role in locomotor control remains to be determined (Ge et al, 2019 ). The role of the 5-HT innervation of the cerebellum in locomotor control is unknown but interestingly: (i) all levels of the cerebellum receive 5-HT fibers; (ii) 5-HT modulates the electrophysiological activity of many cell types in the cerebellum; (iii) the level of cerebellar 5-HT increases during motor activity; and (iv) 5-HT cell metabolism abnormalities were detected in cerebellar ataxia (for review Trouillas, 1993 ; Schweighofer et al, 2004 ).…”

Three-Week Treadmill Exercise Enhances Persistent Inward Currents, Facilitates Dendritic Plasticity, and Upregulates the Excitability of Dorsal Raphe Serotonin Neurons in ePet-EYFP Mice

“…The procedure for whole-cell patch-clamp recording was described in previous study (Dai et al, 2009a ; Ge et al, 2019 ). Briefly, the slices were transferred to a recording chamber mounted in the stage of an upright Olympus BX50 microscope fitted with differential interference contrast (DIC) optics and epifluorescence.…”

“…The main membrane properties measured in current clamp included rheobase (Ith), voltage threshold (Vth), resting membrane potential (Em), input resistance (Rin), AP height and half width, and after-hyperpolarization (AHP) depth, and half-width and number of APs. The calculation of these parameter values had been described in our previous studies (Dai et al, 2009a ; Ge et al, 2019 ; Cheng et al, 2020 ). Briefly, the rheobase (Ith) was determined by step currents with a 0.5-s duration and 5 pA for each step.…”

“…However, the mechanisms by which exercise modulates channels and receptors remain elusive. Persistent inward currents (PICs), long-lasting currents mediated by voltage-gated calcium and sodium channels that inactivate slowly (Powers and Binder, 2003 ; Harvey et al, 2006 ; Dai and Jordan, 2011 ), have been shown to exist in a wide variety of neurons (Schwindt and Crill, 1980 ; Hounsgaard and Kjaerulff, 1992 ; Theiss et al, 2007 ; Dai and Jordan, 2010 ; Muller et al, 2018 ; Ge et al, 2019 ; Revill et al, 2019 ) and play a crucial role in regulating neuronal excitability (Heckman et al, 2008 ; Dai et al, 2018 ). A large number of studies indicate that PICs regulate neuronal excitability through production of plateau potential and bistable firing (Hounsgaard et al, 1984 ; Hounsgaard and Kiehn, 1993 ; Lee and Heckman, 1998 ; Bennett et al, 2001 ), amplification of synaptic inputs (Lee and Heckman, 2000 ; Prather et al, 2001 ; Powers and Heckman, 2017 ), promotion of firing frequency, and initiation of spike (Harvey et al, 2006 ; Kuo et al, 2006 ).…”

“…Previous studies on PICs mainly focused on motoneurons. Recently, we discovered that PICs existed in 5-HT neurons in neonatal mice and played an essential role in regulating the excitability of 5-HT neurons (Ge et al, 2019 ; Cheng et al, 2020 ). However, little is known about exercise modulation of PICs in 5-HT neurons.…”