scholarly journals Distinct roles of light-activated channels TRP and TRPL in photoreceptors of Periplaneta americana

2017 ◽  
Vol 149 (4) ◽  
pp. 455-464 ◽  
Author(s):  
Paulus Saari ◽  
Andrew S. French ◽  
Päivi H. Torkkeli ◽  
Hongxia Liu ◽  
Esa-Ville Immonen ◽  
...  
Keyword(s):  
Information Transfer ◽  
Periplaneta Americana ◽  
Transient Receptor Potential ◽  
Trp Channels ◽  
Light Stimulus ◽  
Gaussian White Noise ◽  
Sensory Information ◽  
Receptor Potential ◽  
Light Sensitivity ◽  
Low Noise

Electrophysiological studies in Drosophila melanogaster and Periplaneta americana have found that the receptor current in their microvillar photoreceptors is generated by two light-activated cationic channels, TRP (transient receptor potential) and TRPL (TRP-like), each having distinct properties. However, the relative contribution of the two channel types to sensory information coding by photoreceptors remains unclear. We recently showed that, in contrast to the diurnal Drosophila in which TRP is the principal phototransduction channel, photoreceptors of the nocturnal P. americana strongly depend on TRPL. Here, we perform a functional analysis, using patch-clamp and intracellular recordings, of P. americana photoreceptors after RNA interference to knock down TRP (TRPkd) and TRPL (TRPLkd). Several functional properties were changed in both knockdown phenotypes: cell membrane capacitance was reduced 1.7-fold, light sensitivity was greatly reduced, and amplitudes of sustained light-induced currents and voltage responses decreased more than twofold over the entire range of light intensities. The information rate (IR) was tested using a Gaussian white-noise modulated light stimulus and was lower in TRPkd photoreceptors (28 ± 21 bits/s) than in controls (52 ± 13 bits/s) because of high levels of bump noise. In contrast, although signal amplitudes were smaller than in controls, the mean IR of TRPLkd photoreceptors was unchanged at 54 ± 29 bits/s1 because of proportionally lower noise. We conclude that TRPL channels provide high-gain/high-noise transduction, suitable for vision in dim light, whereas transduction by TRP channels is relatively low-gain/low-noise and allows better information transfer in bright light.

scholarly journals Physiological temperatures drive glutamate release onto trigeminal superficial dorsal horn neurons

2014 ◽  
Vol 111 (11) ◽  
pp. 2222-2231 ◽  
Author(s):  
Tally M. Largent-Milnes ◽  
Deborah M. Hegarty ◽  
Sue A. Aicher ◽  
Michael C. Andresen
Keyword(s):  
Action Potentials ◽  
Transient Receptor Potential ◽  
Trp Channels ◽  
Glutamate Release ◽  
Sensory Information ◽  
Receptor Potential ◽  
Synaptic Activity ◽  
High Rate ◽  
Sprague Dawley ◽  
Local Circuits

Trigeminal sensory afferent fibers terminating in nucleus caudalis (Vc) relay sensory information from craniofacial regions to the brain and are known to express transient receptor potential (TRP) ion channels. TRP channels are activated by H+, thermal, and chemical stimuli. The present study investigated the relationships among the spontaneous release of glutamate, temperature, and TRPV1 localization at synapses in the Vc. Spontaneous excitatory postsynaptic currents (sEPSCs) were recorded from Vc neurons ( n = 151) in horizontal brain-stem slices obtained from Sprague-Dawley rats. Neurons had basal sEPSC rates that fell into two distinct frequency categories: High (≥10 Hz) or Low (<10 Hz) at 35°C. Of all recorded neurons, those with High basal release rates (67%) at near-physiological temperatures greatly reduced their sEPSC rate when cooled to 30°C without amplitude changes. Such responses persisted during blockade of action potentials indicating that the High rate of glutamate release arises from presynaptic thermal mechanisms. Neurons with Low basal frequencies (33%) showed minor thermal changes in sEPSC rate that were abolished after addition of TTX, suggesting these responses were indirect and required local circuits. Activation of TRPV1 with capsaicin (100 nM) increased miniature EPSC (mEPSC) frequency in 70% of neurons, but half of these neurons had Low basal mEPSC rates and no temperature sensitivity. Our evidence indicates that normal temperatures (35–37°C) drive spontaneous excitatory synaptic activity within superficial Vc by a mechanism independent of presynaptic action potentials. Thus thermally sensitive inputs on superficial Vc neurons may tonically activate these neurons without afferent stimulation.

Restoring light sensitivity using tunable near-infrared sensors

Science ◽  
2020 ◽  
Vol 368 (6495) ◽  
pp. 1108-1113 ◽  
Author(s):  
Dasha Nelidova ◽  
Rei K. Morikawa ◽  
Cameron S. Cowan ◽  
Zoltan Raics ◽  
David Goldblum ◽  
...  
Keyword(s):  
Retinal Degeneration ◽  
Cortical Neurons ◽  
Near Infrared ◽  
Transient Receptor Potential ◽  
Trp Channels ◽  
Receptor Potential ◽  
Light Sensitivity ◽  
Infrared Light ◽  
Temperature Sensitive ◽  
Near Infrared Light

Enabling near-infrared light sensitivity in a blind human retina may supplement or restore visual function in patients with regional retinal degeneration. We induced near-infrared light sensitivity using gold nanorods bound to temperature-sensitive engineered transient receptor potential (TRP) channels. We expressed mammalian or snake TRP channels in light-insensitive retinal cones in a mouse model of retinal degeneration. Near-infrared stimulation increased activity in cones, ganglion cell layer neurons, and cortical neurons, and enabled mice to perform a learned light-driven behavior. We tuned responses to different wavelengths, by using nanorods of different lengths, and to different radiant powers, by using engineered channels with different temperature thresholds. We targeted TRP channels to human retinas, which allowed the postmortem activation of different cell types by near-infrared light.

Intragastric administration of capsiate, a transient receptor potential channel agonist, triggers thermogenic sympathetic responses

2011 ◽  
Vol 110 (3) ◽  
pp. 789-798 ◽  
Author(s):  
Kaori Ono ◽  
Masako Tsukamoto-Yasui ◽  
Yoshiko Hara-Kimura ◽  
Naohiko Inoue ◽  
Yoshihito Nogusa ◽  
...  
Keyword(s):  
Sympathetic Nerve ◽  
Transient Receptor Potential ◽  
Trp Channels ◽  
Low Frequency ◽  
Receptor Potential ◽  
Transient Receptor Potential Channel ◽  
Intragastric Administration ◽  
Brown Adipose ◽  
Reflex Arc ◽  
Transient Receptor

The sympathetic thermoregulatory system controls the magnitude of adaptive thermogenesis in correspondence with the environmental temperature or the state of energy intake and plays a key role in determining the resultant energy storage. However, the nature of the trigger initiating this reflex arc remains to be determined. Here, using capsiate, a digestion-vulnerable capsaicin analog, we examined the involvement of specific activation of transient receptor potential (TRP) channels within the gastrointestinal tract in the thermogenic sympathetic system by measuring the efferent activity of the postganglionic sympathetic nerve innervating brown adipose tissue (BAT) in anesthetized rats. Intragastric administration of capsiate resulted in a time- and dose-dependent increase in integrated BAT sympathetic nerve activity (SNA) over 180 min, which was characterized by an emergence of sporadic high-activity phases composed of low-frequency bursts. This increase in BAT SNA was abolished by blockade of TRP channels as well as of sympathetic ganglionic transmission and was inhibited by ablation of the gastrointestinal vagus nerve. The activation of SNA was delimited to BAT and did not occur in the heart or pancreas. These results point to a neural pathway enabling the selective activation of the central network regulating the BAT SNA in response to a specific stimulation of gastrointestinal TRP channels and offer important implications for understanding the dietary-dependent regulation of energy metabolism and control of obesity.

scholarly journals Characterization Of Selective TRPM8 Ligands And Their Structure Activity Response (S.A.R) Relationship

2010 ◽  
Vol 13 (2) ◽  
pp. 242 ◽  
Author(s):  
Muhammad Azhar Sherkheli ◽  
Angela K. Vogt-Eisele ◽  
Daniel Bura ◽  
Leopoldo R. Beltrán Márques ◽  
Günter Gisselmann ◽  
...  
Keyword(s):  
Ion Channels ◽  
Transient Receptor Potential ◽  
Trp Channels ◽  
Parent Compound ◽  
Receptor Potential ◽  
Basic Research ◽  
Fold Increase ◽  
Ring Structure ◽  
Sensory Nerves ◽  
Transient Receptor Potential Melastatin

PURPOSE: Transient receptor potential melastatin-8 (TRPM8) is an ion channel expressed extensively in sensory nerves, human prostate and overexpressed in a variety of cancers including prostate, breast, lung, colon and skin melanomas. It is activated by innoxious cooling and chemical stimuli. TRPM8 activation by cooling or chemical agonists is reported to induce profound analgesia in neuropathic pain conditions. Known TRPM8 agonists like menthol and icilin cross-activate other thermo-TRP channels like TRPV3 and TRPA1 and mutually inhibit TRPM8. This limits the usefulness of menthol and icilin as TRPM8 ligands. Consequently, the identification of selective and potent ligands for TRPM8 is of high relevance both in basic research and for therapeutic applications. In the present investigation, a group of menthol derivates was characterized. These ligands are selective and potent agonists of TRPM8. Interestingly they do not activate other thermo-TRPs like TRPA1, TRPV1, TRPV2, TRPV3 and TRPV4. These ion channels are also nociceptors and target of many inflammatory mediators. METHODS: Investigations were performed in a recombinant system: Xenopus oocytes microinjected with cRNA of gene of interest were superfused with the test substances after initial responses of known standard agonists. Evoked currents were measured by two-electrode voltage clamp technique. RESULTS: The newly characterized ligands possess an up to six-fold higher potency (EC50 in low µM) and an up to two-fold increase in efficacy compared to the parent compound menthol. In addition, it is found that chemical derivatives of menthol like CPS-368, CPS-369, CPS-125, WS-5 and WS-12 are the most selective ligands for TRPM8. The enhanced activity and selectivity seems to be conferred by hexacyclic ring structure present in all ligands as substances like WS-23 which lack this functional group activate TRPM8 with much lower potency (EC50 in mM) and those with pentacyclcic ring structure (furanone compounds) are totally inactive. CONCLUSION: The new substances activate TRPM8 with a higher potency, efficacy and specificity than menthol and will thus be of importance for the development of pharmacological agents suitable for treatment and diagnosis of certain cancers and as analgesics. STATEMENT OF NOVELTY: The new compounds have an unmatched specificity for TRPM8 ion channels with additional display of high potency and efficacy. Thus these substances are better pharmacological tools for TRPM8 characterization then known compounds and it is suggested that these menthol-derivates may serve as model substances for the development of TRPM8 ligands.

scholarly journals Differential role of TRP channels in prostate cancer

2007 ◽  
Vol 35 (1) ◽  
pp. 133-135 ◽  
Author(s):  
N. Prevarskaya ◽  
M. Flourakis ◽  
G. Bidaux ◽  
S. Thebault ◽  
R. Skryma
Keyword(s):  
Prostate Cancer ◽  
Transient Receptor Potential ◽  
Trp Channels ◽  
Receptor Potential ◽  
Clinical Problem ◽  
Tissue Growth ◽  
Transient Receptor Potential Channels ◽  
Potential Channels ◽  
Differentiation And Proliferation

A major clinical problem with PC (prostate cancer) is the cell's ability to survive and proliferate upon androgen withdrawal. Indeed, deregulated cell differentiation and proliferation, together with the suppression of apoptosis, provides the condition for abnormal tissue growth. Here, we examine the differential role of TRP (transient receptor potential) channels in the control of Ca2+ homoeostasis and growth of PC cells.

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