Electrophysiological and Chemical Properties in Subclassified Acutely Dissociated Cells of Rat Trigeminal Ganglion by Current Signatures

Abstract

Xu S, Ono K, Inenaga K. Electrophysiological and chemical properties in subclassified acutely dissociated cells of rat trigeminal ganglion by current signatures. J Neurophysiol 104: 3451-3461, 2010. First published June 23, 2010 doi:10.1152/jn.00336.2010. In the present study, we subclassified acutely dissociated trigeminal ganglion (TRG) cells of rats using a current signature method in whole cell patch-clamp recordings. Using modified criteria for cell classification for the dorsal root ganglion (DRG), TRG cells were subclassified into nine cell types: 1-5, 7-9, and 13. Types 1, 3, and 7 were in the small cell groups (15-24 m); types 4, 5, and 8 -13 were in the medium cell groups (25-38 m); and type 2 was a mixed group of both cell sizes. Types 1-3, 5, and 7 showed high-input resistance and types 1, 2, and 7 showed more depolarized resting membrane potentials. Types 1, 2, and 5-13 expressed long-duration action potentials (APs), but types 3 and 4 expressed short-duration APs. Sensitivities to capsaicin, protons, and adenosine 5=-triphosphate (ATP) in TRG cell types largely corresponded to DRG cell types. However, different from the matched DRG types, half of TRG type 1 cells were capsaicin insensitive, showing desensitizing proton-induced currents, and types 5, 7, and 9 exhibited slow-desensitizing ATP-induced currents. Types 4, 5, and 8 -13 had nicotine sensitivity, but the other cell types were insensitive. These results indicate that the "current signatures" classification is a useful means to separate TRG cells into internally homogeneous subpopulations that were distinct from other cell types. Furthermore, the data suggest some specific differences in the chemical responsiveness of some cell types between the TRG and DRG.

The distribution of low-threshold TTX-resistant Na+ currents in rat trigeminal ganglion cells

“…Given the hypothesis that variations in cell body expression patterns reflect functional differences between the respective afferents, previous studies suggest there is considerable overlap between TG and DRG regarding sensory neuron modalities. Xu et al (2010), employing the current signature method, documented nine cell body types in the TG, most of which appear very similar, if not identical, to the DRG cell subtypes documented in the laboratories of this author and Brian Cooper (Cardenas et al, 1995;Petruska et al, 2000). However, it seems probable that the TG neurons include types not found in the DRG, since TG neurons innervate tissues not present in the trunk and limbs.…”

Optogenetic Patterning of Whisker-Barrel Cortical System in Transgenic Rat Expressing Channelrhodopsin-2

“…Of them, five types of cells have larger cell bodies. And four larger type cells showed long-duration APs, while the remaining one had short-duration APs [17]. Such variable electrophysiological behavior is probably dependent on the different membrane properties generated by ion channels.…”

The Effect of Pungent and Tingling Compounds from Piper nigrum L. on Background K+ Currents

“…To elicit these characteristic impressions, sensory active compound from black peppercorns activate trigeminal neurons, which are primary sensory neurons whose bodies reside in the trigeminal ganglion (Viana, 2011). These cells are specialized in conveying information regarding different sensory events, such as light pressure, heat, cold, as well as helping to provide information regarding the chemical characteristics of the environment (Xu et al, 2010; Viana, 2011). The functionally diverse populations of trigeminal neurons have been classified according to their size, the neurotransmitters they release, their “current signature” (Xu et al, 2010), as well as their pharmacological profile (Spehr et al, 2004).…”

“…These cells are specialized in conveying information regarding different sensory events, such as light pressure, heat, cold, as well as helping to provide information regarding the chemical characteristics of the environment (Xu et al, 2010; Viana, 2011). The functionally diverse populations of trigeminal neurons have been classified according to their size, the neurotransmitters they release, their “current signature” (Xu et al, 2010), as well as their pharmacological profile (Spehr et al, 2004). To be able to react to chemical stimuli trigeminal neurons rely on chemosensitive proteins expressed on their membranes, mostly ion channels (Gerhold and Bautista, 2009; Viana, 2011).…”