Liu L, Simon S A
Department of Neurobiology, Duke University Medical Center, Durham, NC 27710.
Proc Natl Acad Sci U S A. 1994 Jan 18;91(2):738-41. doi: 10.1073/pnas.91.2.738.
A subpopulation of pain fibers are activated by capsaicin, the ingredient in red peppers that produces a burning sensation when eaten or placed on skin. Previous studies on dorsal root ganglion neurons indicated that capsaicin activates sensory nerves via a single slowly activating and inactivating inward current. In rat trigeminal neurons, we identified a second capsaicin-activated inward current. This current can be distinguished from the slow one in that it rapidly activates and inactivates, requires Ca2+ for activation, and is insensitive to the potent capsaicin agonist resiniferatoxin. The rapid current, like the slower one, is inhibited by ruthenium red and capsazepine. The two capsaicin-activated inward currents share many similarities with the two inward currents activated by lowering the pH to 6.0. These similarities include kinetics, reversal potentials, responses to Ca2+, and inhibition by ruthenium red and capsazepine. These results suggest that acidic stimuli may be an endogenous activator of capsaicin-gated currents and therefore may rationalize why pain is produced when the plasma acidity is increased, as occurs during ischemia and inflammation.
一类痛觉纤维可被辣椒素激活，辣椒素是红辣椒中的一种成分，食用或涂抹在皮肤上时会产生灼烧感。先前对背根神经节神经元的研究表明，辣椒素通过单一缓慢激活和失活的内向电流激活感觉神经。在大鼠三叉神经元中，我们发现了第二种辣椒素激活的内向电流。这种电流与缓慢激活的电流不同，它快速激活和失活，激活需要Ca2+，并且对强效辣椒素激动剂树脂毒素不敏感。快速电流与缓慢电流一样，可被钌红和辣椒平抑制。两种辣椒素激活的内向电流与通过将pH值降至6.0激活的两种内向电流有许多相似之处。这些相似之处包括动力学、反转电位、对Ca2+的反应以及被钌红和辣椒平抑制。这些结果表明，酸性刺激可能是辣椒素门控电流的内源性激活剂，因此可以解释为什么在缺血和炎症期间血浆酸度增加时会产生疼痛。
