Temporal and spatial summation of laser heat stimuli in cultured nociceptive neurons of the rat

• Verfasst von: Jubileum, Elisabeth [VerfasserIn]
• Verfasst von: Binzen, Uta [VerfasserIn]
• Verfasst von: Treede, Rolf-Detlef [VerfasserIn]
• Verfasst von: Greffrath, Wolfgang [VerfasserIn]
• Titel: Temporal and spatial summation of laser heat stimuli in cultured nociceptive neurons of the rat
• Titelzusatz: sensory physiology
• Verf.angabe: Elisabeth Jubileum, Uta Binzen, Rolf-Detlef Treede, Wolfgang Greffrath
• E-Jahr: 2022
• Jahr: 22 July 2022
• Umfang: 17 S.
• Illustrationen: Illustrationen
• Fussnoten: Gesehen am 25.09.2023
• Titel Quelle: Enthalten in: Pflügers Archiv
• Ort Quelle: Berlin : Springer, 1868
• Jahr Quelle: 2022
• Band/Heft Quelle: 474(2022), 9 vom: Sept., Seite 1003-1019
• ISSN Quelle: 1432-2013
• DOI: doi:10.1007/s00424-022-02728-1
• Datenträger: Online-Ressource
• Sprache: eng
• Sach-SW: Calcium imaging
• Sach-SW: Heat pain
• Sach-SW: Nociception
• Sach-SW: Transduction
• Sach-SW: TRPV
• K10plus-PPN: 1860242413

Abstract

We studied the efficacy of a near-infrared laser (1475 nm) to activate rat dorsal root ganglion (DRG) neurons with short punctate radiant heat pulses (55 µm diameter) and investigated temporal and spatial summation properties for the transduction process for noxious heat at a subcellular level. Strength-duration curves (10-80 ms range) indicated a minimum power of 30.2mW for the induction of laser-induced calcium transients and a chronaxia of 13.9 ms. However, threshold energy increased with increasing stimulus duration suggesting substantial radial cooling of the laser spot. Increasing stimulus duration demonstrated suprathreshold intensity coding of calcium transients with less than linear gains (Stevens exponents 0.29/35mW, 0.38/60mW, 0.46/70mW). The competitive TRPV1 antagonist capsazepine blocked responses to short near-threshold stimuli and significantly reduced responses to longer duration suprathreshold heat. Heating 1/3 of the soma of a neuron was sufficient to induce calcium transients significantly above baseline (p < 0.05), but maximum amplitude was only achieved by centering the laser over the entire neuron. Heat-induced calcium increase was highest in heated cell parts but rapidly reached unstimulated areas reminiscent of spreading depolarization and opening of voltage-gated calcium channels. Full intracellular equilibrium took about 3 s, consistent with a diffusion process. In summary, we investigated transduction mechanisms for noxious laser heat pulses in native sensory neurons at milliseconds temporal and subcellular spatial resolution and characterized strength duration properties, intensity coding, and spatial summation within single neurons. Thermal excitation of parts of a nociceptor spread via both membrane depolarization and intracellular calcium diffusion.