Comparison of currents activated by noxious heat in rat and chicken primary sensory neurons.
The vanilloid receptor 1 (VR1) gene is responsible for both capsaicin-, and low threshold (LT) noxious heat-sensitivity in mammalian primary sensory neurons. Although, birds lack capsaicin-sensitivity they express LT noxious heat-sensitivity. Here, we compared LT noxious heat-activated whole-cell currents produced by rat and chicken cultured dorsal root ganglion neurons in order to find out the similarities and differences in the LT noxious heat transduction mechanisms between the two species. No significant differences between rat and chicken neurons were found in the mean cell diameter of the LT noxious heat-sensitive cells (20.4+/-0.8 microm, n=19 and 20.6+/-0.6 microm, n=11, respectively) and the average threshold (45.7+/-0.5 degrees C, n=19 and 46.1+/-0.7 degrees C, n=11, respectively) and peak amplitude (-2.9+/-0.6 nA, n=19 and -2.1+/-0.6 nA, n=11, respectively) of the heat-evoked responses. The current-voltage curves of the responses both in rat and chicken cells reversed at the same range (-19.5+/-3.8 mV, n=4 and -15.5+/-1. 2 mV, n=3, respectively) and showed strong outward rectification at negative membrane potentials. While all LT noxious heat-sensitive rat cells responded to capsaicin, none of the chicken neurons produced detectable response to it. These findings suggest that a VR1 homologue which lacks to sequence for capsaicin-sensitivity is possibly the LT noxious heat transducer in chicken.
Nagy
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I
Department of Anaesthetics and Intensive Care, Imperial College School of Medicine, Chelsea and Westminster Hospital, 369 Fulham Road, SW10 9NH, London, UK. i.nagy@ic.ac.uk
Rang
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H
D000818:Animals; D002211:Capsaicin / Q000494:pharmacology; D002478:Cells, Cultured; D002645:Chickens; D004553:Electric Conductivity; D005727:Ganglia, Spinal / Q000166:cytology*; D006358:Hot Temperature / Q000009:adverse effects*; D008564:Membrane Potentials / Q000187:drug effects; D009475:Neurons, Afferent / Q000187:drug effects / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D051381:Rats; D011955:Receptors, Drug / Q000378:metabolism; D013045:Species Specificity; D050916:TRPV Cation Channels
D011955:Receptors, Drug; D050916:TRPV Cation Channels; C494484:TRPV1 receptor; D002211:Capsaicin