Biology subjects

Romero, G. E.

Publications and source records attributed to Romero, G. E..

4 recordsLinked to original sources

bioRxiv2024

The auditory midbrain mediates tactile vibration sensing

Vibrations are ubiquitous in nature, shaping behavior across the animal kingdom. For mammals, mechanical vibrations acting on the body are detected by mechanoreceptors of the skin and deep tissues and processed by the somatosensory system, while sound waves traveling through air are captured by the cochlea and encoded in the auditory system. Here, we report that mechanical vibrations detected by the bodys Pacinian corpuscle neurons, which are unique in their ability to entrain to high frequency (40-1000 Hz) environmental vibrations, are prominently encoded by neurons in the lateral cortex of the inferior colliculus (LCIC) of the midbrain. Remarkably, most LCIC neurons receive convergent Pacinian and auditory input and respond more strongly to coincident tactile-auditory stimulation than to either modality alone. Moreover, the LCIC is required for behavioral responses to high frequency mechanical vibrations. Thus, environmental vibrations captured by Pacinian corpuscles are encoded in the auditory midbrain to mediate behavior.

neuroscience↗

bioRxiv2022

Kv7 channel antagonists block glycine receptors

XE991 (10,10-bis(4-pyridinylmethyl)-9(10H)-anthracenone) is currently the most widely used and specific antagonist of the Kv7 (KCNQ) family of K+ channels. We report an unexpected antagonistic effect of this drug on ionotropic glycine receptors. In recordings of synaptic transmission in two brainstem nuclei (the medial nucleus of the trapezoid body and the dorsal cochlear nucleus), 10 M XE991, a concentration typical for Kv7 studies in brain tissue, inhibited evoked glycinergic inhibitory postsynaptic currents (IPSCs) without altering paired-pulse ratio, and also reduced the amplitude of glycinergic miniature IPSCs. These results are indicative of a direct effect of the drug on postsynaptic glycine receptors. XE991 also produced dose-dependent block of the response to exogenously applied glycine, to a degree comparable to the block of synaptic transmission. Moreover, the drug inhibited homomeric glycine receptors expressed on presynaptic membrane of the calyx of Held. The degree of block was independent of glycine concentration, suggesting an allosteric interaction. The effects of XE991 on glycine responses are not likely to reflect block of the glycine-activated Cl- channels themselves, because block was voltage independent, and because GABA-activated Cl- currents were resistant to XE991 at concentrations up to 100 {micro}M. Linopirdine, but not retigabine, also antagonized glycine receptor currents. Given the prevalence of glycine receptor signaling in the brain, these observations should be taken into account in studies of the roles of Kv7 channels in neural circuit function and disease.

neuroscience↗

bioRxiv2021

Distinct forms of synaptic plasticity during ascending vs. descending control of medial olivocochlear efferent neurons

Activity in each brain region is shaped by the convergence of ascending and descending axonal pathways, and the balance and characteristics of these determine neural output. The medial olivocochlear (MOC) efferent system is part of a reflex arc that critically controls auditory sensitivity. Multiple central pathways contact MOC neurons, raising the question of how a reflex arc could be engaged by diverse inputs. We examined functional properties of synapses onto brainstem MOC neurons from ascending (ventral cochlear nucleus, VCN), and descending (inferior colliculus, IC) sources in mice using an optogenetic approach. We found that these pathways exhibited opposing forms of short-term plasticity, with VCN input showing depression and IC input showing marked facilitation. By using a conductance clamp approach, we found that combinations of facilitating and depressing inputs enabled firing of MOC neurons over a surprisingly wide dynamic range, suggesting an essential role for descending signaling to a brainstem nucleus.

neuroscience↗

bioRxiv2020

Discovery of a novel inhibitory neuron class, the L-Stellate cells of the cochlear nucleus

Auditory processing depends upon inhibitory signaling by interneurons, even at its earliest stages in the ventral cochlear nucleus (VCN). Remarkably, to date only a single subtype of inhibitory neuron has been documented in the VCN, a projection neuron termed the D-stellate cell. With the use of a transgenic mouse line, optical clearing and imaging techniques, combined with electrophysiological tools, we revealed a population of glycinergic cells in the VCN distinct from the D-stellate cell. These novel multipolar glycinergic cells were smaller in soma size and dendritic area, but over 10-fold more numerous than D-stellate cells. They were activated by auditory nerve fibers and T-stellate cells, and made local inhibitory synaptic contacts on principal cells of the VCN. Given their abundance, combined with their narrow dendritic fields and axonal projections, it is likely that these neurons, here termed L-stellate cells, play a significant role in frequency-specific processing of acoustic signals.

neuroscience↗