Related Experiment Videos
Selective opioid inhibition of small nociceptive neurons
A Taddese1, S Y Nah, E W McCleskey
1Vollum Institute, Oregon Health Sciences University, Portland 97201, USA.
Abstract:
Opioid analgesia, the selective suppression of pain without effects on other sensations, also distinguishes between different types of pain: severe, persistent pain is potently inhibited by opioids, but they fail to cohceal the sensation of a pinprick. The cellular basis for this specificity was analyzed by means of patch-clamp experiments performed on fluorescently labeled nociceptive neurons (nociceptors) that innervate rat tooth pulp. Activation of the mu opioid receptor inhibited calcium channels on almost all small nociceptors but had minimal effect on large nociceptors. Somatostatin had the opposite specificity, preferentially inhibiting calcium channels on the large cells. Because persistent pain is mediated by slow-conducting, small nociceptors, opioids are thus likely to inhibit neurotransmitter release only at those primary synapses specialized for persistent pain.
Insights
Opioid pain relief is specific, targeting severe pain signals from small nerve cells while sparing sharp pain sensations. This selectivity stems from mu opioid receptors primarily affecting small nociceptors, crucial for persistent pain pathways.
Area of Science:
- Neuroscience
- Pharmacology
Background:
- Opioid analgesia selectively suppresses pain without affecting other sensations.
- Opioids effectively inhibit severe, persistent pain but not sharp sensations like a pinprick.
Purpose of the Study:
- To analyze the cellular basis for opioid analgesia's specificity.
- To investigate the differential effects of opioids on various nociceptor types.
Main Methods:
- Patch-clamp experiments were conducted on fluorescently labeled rat nociceptive neurons (nociceptors).
- The study focused on nociceptors innervating rat tooth pulp.
Main Results:
- Activation of the mu opioid receptor inhibited calcium channels in nearly all small nociceptors.
- Mu opioid receptor activation had minimal effect on large nociceptors.
- Somatostatin exhibited opposite specificity, inhibiting large cells preferentially.
Conclusions:
- Opioids likely inhibit neurotransmitter release specifically at synapses for persistent pain.
- This selectivity is attributed to the preferential action of mu opioid receptors on small nociceptors, which mediate persistent pain.