TRPM8 mRNA Is Expressed in a Subset of Cold-Responsive Trigeminal Neurons From Rat

2003 ◽  
Vol 90 (1) ◽  
pp. 515-520 ◽  
Author(s):  
Michele L. Nealen ◽  
Michael S. Gold ◽  
Paul D. Thut ◽  
Michael J. Caterina
Keyword(s):  
Cold Temperatures ◽  
Trigeminal Neurons ◽  
Cold Receptors ◽  
Electrophysiological Studies ◽  
Ionic Mechanisms ◽  
Cold Sensitive ◽  
Low Threshold ◽  
Ion Channel Proteins ◽  
Trigeminal Ganglion Neurons ◽  
Ganglion Neurons

Recent electrophysiological studies of cultured dorsal root and trigeminal ganglion neurons have suggested that multiple ionic mechanisms underlie the peripheral detection of cold temperatures. Several candidate “cold receptors,” all of them ion channel proteins, have been implicated in this process. One of the most promising candidates is TRPM8, a nonselective cationic channel expressed in a subpopulation of sensory neurons that is activated both by decreases in temperature and the cooling compound menthol. However, evidence for the expression of TRPM8 in functionally defined cold-sensitive neurons has been lacking. Here, we combine fluorometric calcium imaging of cultured rat trigeminal neurons with single-cell RT-PCR to demonstrate that there are distinct subpopulations of cold responsive neurons and that TRPM8 likely contributes to cold transduction in one of them. TRPM8 is preferentially expressed within a subset of rapidly responsive, low-threshold (approximately 30°C), cold-sensitive neurons. A distinct class of slowly responsive cold-sensitive neurons that is activated at lower temperatures (approximately 20°C) generally lacks detectable TRPM8 mRNA. Together with previous findings, our data support the notion that cold responsive neurons are functionally heterogeneous.

scholarly journals Precise Temporal Responses in Whisker Trigeminal Neurons

2004 ◽  
Vol 92 (1) ◽  
pp. 665-668 ◽  
Author(s):  
Lauren M. Jones ◽  
SooHyun Lee ◽  
Jason C. Trageser ◽  
Daniel J. Simons ◽  
Asaf Keller
Keyword(s):  
Trigeminal Ganglion ◽  
Neural Representation ◽  
Stimulus Information ◽  
Robust Coding ◽  
Complex Stimuli ◽  
Trigeminal Neurons ◽  
Response Profiles ◽  
Trigeminal Ganglion Neurons ◽  
Ganglion Neurons ◽  
Spike Patterns

The ability of rats using their whiskers to perform fine tactile discrimination rivals that of humans using their fingertips. Rats must perform these discriminations rapidly and accurately while palpating the environment with their whiskers. This suggests that whisker-derived inputs produce a robust and reliable code, capable of capturing complex, high-frequency information. The first neural representation of whisker-derived stimulus information is in primary afferent neurons of the trigeminal ganglion. Here we demonstrate that there is a continuum of direction-dependent response profiles in trigeminal neurons and provide the first quantitative analysis of the encoding of complex stimuli by these neurons. We show that all classes of trigeminal ganglion neurons respond with highly reproducible temporal spike patterns to transient stimuli. Such a robust coding mechanism may allow rapid perception of complex tactile features.

scholarly journals Acute corneal epithelial debridement unmasks the corneal stromal nerve responses to ocular stimulation in rats: implications for abnormal sensations of the eye

2017 ◽  
Vol 117 (5) ◽  
pp. 1935-1947 ◽  
Author(s):  
Harumitsu Hirata ◽  
Kamila Mizerska ◽  
Valentina Dallacasagrande ◽  
Victor H. Guaiquil ◽  
Mark I. Rosenblatt
Keyword(s):  
Epithelial Cell ◽  
Sensory Information ◽  
Sensory Transduction ◽  
High Threshold ◽  
Nerve Terminals ◽  
Transduction Mechanisms ◽  
Cell Layers ◽  
Cold Sensitive ◽  
Low Threshold ◽  
Ganglion Neurons

It is widely accepted that the mechanisms for transducing sensory information reside in the nerve terminals. Occasionally, however, studies have appeared demonstrating that similar mechanisms may exist in the axon to which these terminals are connected. We examined this issue in the cornea, where nerve terminals in the epithelial cell layers are easily accessible for debridement, leaving the underlying stromal (axonal) nerves undisturbed. In isoflurane-anesthetized rats, we recorded extracellularly from single trigeminal ganglion neurons innervating the cornea that are excited by ocular dryness and cooling: low-threshold (<2°C cooling) and high-threshold (>2°C) cold-sensitive plus dry-sensitive neurons playing possible roles in tearing and ocular pain. We found that the responses in both types of neurons to dryness, wetness, and menthol stimuli were effectively abolished by the debridement, indicating that their transduction mechanisms lie in the nerve terminals. However, some responses to the cold, heat, and hyperosmolar stimuli in low-threshold cold-sensitive plus dry-sensitive neurons still remained. Surprisingly, the responses to heat in approximately half of the neurons were augmented after the debridement. We were also able to evoke these residual responses and follow the trajectory of the stromal nerves, which we subsequently confirmed histologically. The residual responses always disappeared when the stromal nerves were cut at the limbus, suggesting that the additional transduction mechanisms for these sensory modalities originated most likely in stromal nerves. The functional significance of these residual and enhanced responses from stromal nerves may be related to the abnormal sensations observed in ocular disease. NEW & NOTEWORTHY In addition to the traditional view that the sensory transduction mechanisms exist in the nerve terminals, we report here that the proximal axons (stromal nerves in the cornea from which these nerve terminals originate) may also be capable of transducing sensory information. We arrived at this conclusion by removing the epithelial cell layers of the cornea in which the nerve terminals reside but leaving the underlying stromal nerves undisturbed.

scholarly journals Differential mechanisms of cold sensitivity in mouse trigeminal and vagal ganglion neurons

2021 ◽  
Author(s):  
Katharina Gers-Barlag ◽  
Pablo Hernández-Ortego ◽  
Eva Quintero ◽  
Félix Viana
Keyword(s):  
Cold Sensitivity ◽  
Cold Temperatures ◽  
Retrograde Labelling ◽  
Critical Elements ◽  
Thermally Driven ◽  
Cold Sensitive ◽  
Ganglion Neurons ◽  
Vagal Ganglia

Thermal signals are critical elements in the operation of interoceptive and exteroceptive neural circuits, essential for triggering thermally-driven reflexes and conscious behaviors. A fraction of cutaneous and visceral sensory endings are activated by cold temperatures. Compared to somatic (DRG and TG) neurons, little is known about the mechanisms underlying cold sensitivity of visceral vagal neurons. We used pharmacological and genetic tools for a side-by-side characterization of cold-sensitive (CS) neurons in adult mouse trigeminal (TG) and vagal ganglia (VG). We found that CS neurons are more abundant in VG than in TG. In both ganglia, sensitivity to cold varied widely and was enhanced by the potassium channel blocker 4-AP. The majority of CS neurons in VG co-express TRPA1 markers and cold-evoked responses are severely blunted in Trpa1 KO mice, with little impact of TRPM8 deletion or pharmacological TRPM8 blockade. Consistent with these findings, the expression of TRPM8-positive neurons was low in VG and restricted to the rostral jugular ganglion. In vivo retrograde labelling of airway-innervating vagal neurons demonstrated their enhanced cold sensitivity and a higher expression of TRPA1 compared to neurons innervating the stomach wall. In contrast, the majority of CS TG neurons co-express TRPM8 markers and their cold sensitivity is reduced after TRPM8 deletion or blockade. However, pharmacological or genetic reduction of TRPA1 showed that these channels contribute significantly to their cold sensitivity in TG. In both ganglia, a fraction of CS neuron respond to cooling by a mechanism independent of TRPA1 or TRPM8 yet to be characterized.

Effects of WIN 55, 212-2 onI K current in cultured trigeminal ganglion neurons of rat

2005 ◽  
Vol 25 (2) ◽  
pp. 124-126
Author(s):  
Ming Zhangyin ◽  
Tan Yan ◽  
Fu Hui ◽  
Cao Xuehong ◽  
Pan Jianping ◽  
...  
Keyword(s):  
Trigeminal Ganglion ◽  
K Current ◽  
Trigeminal Ganglion Neurons ◽  
Ganglion Neurons ◽  
Win 55

5HT Increases Excitability of Nociceptor-Like Rat Dorsal Root Ganglion Neurons Via cAMP-Coupled TTX-Resistant Na+Channels

2001 ◽  
Vol 86 (1) ◽  
pp. 241-248 ◽  
Author(s):  
Luz M. Cardenas ◽  
Carla G. Cardenas ◽  
Reese S. Scroggs
Keyword(s):  
Dorsal Root Ganglion ◽  
Signaling Pathway ◽  
Dorsal Root ◽  
Phosphodiesterase Inhibitor ◽  
Dorsal Root Ganglion Neurons ◽  
Receptor Coupling ◽  
Low Threshold ◽  
Ganglion Neurons ◽  
Serotonergic Modulation

The physiological effects of 5HT receptor coupling to TTX-resistant Na+ current, and the signaling pathway involved, was studied in a nociceptor-like subpopulation of rat dorsal root ganglion (DRG) cells (type 2), which can be identified by expression of a low-threshold, slowly inactivating A-current. The 5HT-mediated increase in TTX-resistant Na+ current in type 2 DRG cells was mimicked and occluded by 10 μM forskolin. Superfusion of type 2 DRG cells on the outside with 1 mM 8-bromo-cAMP or chlorophenylthio-cAMP (CPT-cAMP) increased the Na+ current, but less than 5HT itself. However, perfusion of the cells inside with 2 mM CPT-cAMP strongly increased the amplitude of control Na+currents and completely occluded the effect of 5HT. Thus it appears that the signaling pathway includes cAMP. The phosphodiesterase inhibitor 3-isobutyl-l-methylxanthine (200 μM) also mimicked the effect of 5HT on Na+ current, suggesting tonic adenylyl cyclase activity. 5HT reduced the amount of current required to evoke action potentials in type 2 DRG cells, suggesting that 5HT may lower the threshold for activation of nociceptor peripheral receptors. The above data suggest that serotonergic modulation of TTX-resistant Na+channels through a cAMP-dependent signaling pathway in nociceptors may participate in the generation of hyperalgesia.

Capsaicin and nicotine both activate a subset of rat trigeminal ganglion neurons

1996 ◽  
Vol 270 (6) ◽  
pp. C1807-C1814 ◽  
Author(s):  
L. Liu ◽  
S. A. Simon
Keyword(s):  
Trigeminal Ganglion ◽  
Acetylcholine Receptors ◽  
Ganglion Cells ◽  
Whole Cell Patch Clamp ◽  
Current Voltage ◽  
Trigeminal Ganglion Neurons ◽  
Ganglion Neurons ◽  
Relationship Of ◽  
Current Voltage Relationship ◽  
Voltage Relationship

Nicotine and capsaicin produce many similar physiological responses that include pain, irritation, and vasodilation. To determine whether neuronal nicotine acetylcholine receptors (nAChR) are present on capsaicin-sensitive neurons, whole cell patch-clamp recordings were performed on rat trigeminal ganglion cells. It was found that approximately 20% of the total number of neurons tested was activated by both 100 microM nicotine and 1 nM capsaicin. Other subsets of neurons were activated by only one of these compounds, whereas a fourth subset was not activated by either compound. At -60 mV, the magnitude of the capsaicin-activated currents was about three times larger than the magnitude of the nicotine-activated currents. The current-voltage relationship of the nAChR exhibited marked rectification, such that for voltages > or = 0 mV the current was essentially zero. In contrast, the current-voltage relationship of the capsaicin-activated current was ohmic from +/- 60 mV. These data indicate the existence of subsets of capsaicin-sensitive afferent neurons.

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