Three kinds of current in response to substance P in bullfrog DRG neurons.
In response to SP applied externally, neurons freshly isolated from bullfrog dorsal root ganglion (DRG) showed three kinds of current (I(SP)), i.e. slow, fast and moderately activating I(SP)s. All the three kinds of I(SP) were inward currents, and were completely blocked by either peptide antagonist of SP receptor spantide or non-peptide antagonist of SP receptor WIN51708. The slow activating I(SP) showed slow kinetic features. Replacement of NaCl in external solution by NMDG had no effect on this kind of I(SP), while Ba(2+) abolished it almost completely, thus the ionic mechanism underlying slow activating I(SP) was deduced to be the closure of K(+) channels. The fast activating I(SP) in bullfrog DRG neurons, just as in rat DRG neurons, was proved to be caused by the opening of Na(+) preferring non-selective cation channel, for it was abolished almost completely by replacement of NaCl in external solution with equimolar NMDG. The moderately activating I(SP) was similar to the fast activating I(SP) in current configuration, however, its kinetic characteristics lay between those of fast and slow activating I(SP)s. Either NMDG or Ba(2+) suppressed this kind of I(SP) partially. Therefore the moderately activating I(SP) might be mediated by non-selective cation channel. We used repatch technique to explore the intracellular mechanism underlying the three kinds of I(SP) and found that the three kinds of I(SP) were caused by the activity of either G-protein coupled channel (slow activating I(SP)) or directly opened channel (fast activating I(SP)) or both (moderately activating I(SP) ).
Yang
Yun-Lei
YL
Department of Molecular and Cellular Neurobiology, Tongji Medical College, Huazhong University of Science and Technology, 13 Hangkong Road, Wuhan 430030, China.
Yao
Kai-Hui
KH
Gu
Yuan-Zheng
YZ
Guan
Bing-Cai
BC
Li
Zhi-Wang
ZW
D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine / Q000494:pharmacology; D000700:Analgesics / Q000494:pharmacology; D000704:Analysis of Variance; D000731:Androstanes / Q000494:pharmacology; D000818:Animals; D001464:Barium / Q000494:pharmacology; D001562:Benzimidazoles / Q000494:pharmacology; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D004553:Electric Conductivity; D004594:Electrophysiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005727:Ganglia, Spinal / Q000187:drug effects / Q000502:physiology*; D006153:Guanosine Diphosphate / Q000031:analogs & derivatives* / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D009474:Neurons / Q000187:drug effects* / Q000502:physiology; D018408:Patch-Clamp Techniques / Q000379:methods; D011892:Rana catesbeiana; D011930:Reaction Time; D013373:Substance P / Q000819:agonists / Q000031:analogs & derivatives* / Q000494:pharmacology*; D013873:Thionucleotides / Q000494:pharmacology
D000700:Analgesics; D000731:Androstanes; D001562:Benzimidazoles; D004791:Enzyme Inhibitors; D013873:Thionucleotides; C086111:WIN 51708; D006153:Guanosine Diphosphate; D001464:Barium; D013373:Substance P; C023427:guanosine 5'-O-(2-thiodiphosphate); D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; C042867:spantide