Adult spinal V2a interneurons show increased excitability and serotonin-dependent bistability.

In mice, most studies of the organization of the spinal central pattern generator (CPG) for locomotion, and its component neuron classes, have been performed on neonatal [postnatal day (P)2-P4] animals. While the neonatal spinal cord can generate a basic locomotor pattern, it is often argued that the CPG network is in an immature form whose detailed properties mature with postnatal development. Here, we compare intrinsic properties and serotonergic modulation of the V2a class of excitatory spinal interneurons in behaviorally mature (older than P43) mice to those in neonatal mice.

A comparison of serotonin neuromodulation of mouse spinal V2a interneurons using perforated patch and whole cell recording techniques.

Whole cell recordings (WCRs) are frequently used to study neuronal properties, but may be problematic when studying neuromodulatory responses, due to dialysis of the cell's cytoplasm. Perforated patch recordings (PPR) avoid cellular dialysis and might reveal additional modulatory effects that are lost during WCR. We have previously used WCR to characterize the responses of the V2a class of Chx10-expressing neurons to serotonin (5-HT) in the neonatal mouse spinal cord (Zhong et al.

Postnatal development of dendrodendritic inhibition in the Mammalian olfactory bulb.

The mitral-granule cell (MC-GC) reciprocal synapse is an important source of auto- and lateral-inhibition in the olfactory bulb (OB), and this local inhibition is critical for odor discrimination. We may gain insight into the role of MC autoinhibition in olfaction by correlating the functional development of the autoinhibition with the postnatal development of olfactory function. We have studied the functional development of the MC-GC reciprocal synapse using whole-cell patch-clamp recordings from MCs and GCs in acute OB slices from 3- to 30-day-old rats.

Spatiotemporal dynamics of rhythmic spinal interneurons measured with two-photon calcium imaging and coherence analysis.

In rhythmic neural circuits, a neuron often fires action potentials with a constant phase to the rhythm, a timing relationship that can be functionally significant. To characterize these phase preferences in a large-scale, cell type-specific manner, we adapted multitaper coherence analysis for two-photon calcium imaging. Analysis of simulated data showed that coherence is a simple and robust measure of rhythmicity for calcium imaging data.

Electrophysiological characterization of V2a interneurons and their locomotor-related activity in the neonatal mouse spinal cord.

The V2a class of Chx10-expressing interneurons has been implicated in frequency-dependent control of left-right phase during locomotion in the mouse. We have used the Chx10::CFP mouse line to further investigate the properties and locomotion-related activity of V2a interneurons in the isolated neonatal spinal cord. V2a interneurons can be divided into three classes, based on their tonic, phasic, or delayed-onset responses to step depolarization.

Activity of Hb9 interneurons during fictive locomotion in mouse spinal cord.

Hb9 interneurons (Hb9 INs) are putative components of the mouse spinal locomotor central pattern generator (CPG) and candidates for the rhythm-generating kernel. Studies in slices and hemisected spinal cords showed that Hb9 INs display TTX-resistant membrane potential oscillations, suggesting a role in rhythm generation. To further investigate the roles of Hb9 INs in the locomotor CPG, we used two-photon calcium imaging in the in vitro isolated whole neonatal mouse spinal cord preparation to record the activity of Hb9 INs, which were subsequently stained for unambiguous genetic identification.

Contrasting short-term plasticity at two sides of the mitral-granule reciprocal synapse in the mammalian olfactory bulb.

The mitral-granule reciprocal synapse shapes the response of the olfactory bulb to odour stimuli by mediating lateral and reciprocal inhibition. We investigated the short-term plasticity of both the mitral-to-granule excitatory synapse and the granule-to-mitral inhibitory synapse in rat olfactory bulb slices, using whole-cell patch clamp recordings. The granule-to-mitral inhibitory synapse invariably exhibited paired-pulse depression at interstimulus intervals of less than a second, while the mitral-to-granule excitatory synapse showed heterogeneous responses, which on average yielded a moderate facilitation.