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ATP responses in human C nociceptors.
Marita Hilliges1, Christian Weidner, Martin Schmelz
1Department of Clinical Neurophysiology, University of Uppsala, S-75185 Uppsala, Sweden. marita.hilliges@ofa.ki.se
Pain
|July 6, 2002
Summary
Adenosine triphosphate (ATP) activates human C-nociceptors, including both mechano-responsive and mechano-insensitive nerve fibers, without causing sensitization to heat or mechanical stimuli. This study investigated ATP
Area of Science:
- Neuroscience
- Pain Research
- Sensory Physiology
Background:
- Nociceptive C-fibers are crucial for transmitting pain signals.
- Adenosine triphosphate (ATP) is implicated as a signaling molecule in pain pathways.
- Understanding C-fiber responses to ATP is vital for pain management strategies.
Purpose of the Study:
- To investigate the responsiveness of different classes of human C-nociceptors to adenosine triphosphate (ATP).
- To determine if ATP activates mechano-responsive versus mechano-insensitive C-fibers.
- To assess the sensitizing effects of ATP on C-fibers.
Main Methods:
- Microelectrode recordings of impulse activity in cutaneous fascicles of the peroneal nerve in healthy human subjects.
- Identification of mechano-heat responsive (CMH), heat-responsive (CH), and mechano-insensitive/heat-insensitive (CM(i)H(i)) C-units.
- Controlled intradermal injections of adenosine triphosphate (ATP) and saline, with focus on post-injection responses.
Main Results:
- ATP activated both mechano-responsive (63%) and mechano-insensitive (64%) C-nociceptor units.
- Mechano-insensitive units, including heat-responsive (CH) and mechano-insensitive/heat-insensitive (CM(i)H(i)) types, were excited by ATP.
- ATP responses exhibited a delayed onset, peaked within minutes, and persisted for up to 20 minutes; responses were dose-dependent.
- No heat or mechanical sensitization of C-fibers was observed following ATP injection.
Conclusions:
- High concentrations of ATP activate C-nociceptors in healthy human skin, irrespective of their mechanosensitivity.
- ATP does not appear to sensitize human C-fibers to mechanical or thermal stimuli.
- Further research is needed to elucidate the mechanisms underlying ATP-evoked C-fiber activation.