TY - JOUR
T1 - Cutaneous injection of the capsaicin analogue, NE-21610, produces analgesia to heat but not to mechanical stimuli in man
AU - Davis, Karen D.
AU - Meyer, Richard A.
AU - Turnquist, Jennifer L.
AU - Filloon, Tom G.
AU - Pappagallo, Marco
AU - Campbell, James N.
PY - 1995/4
Y1 - 1995/4
N2 - Intradermal injection of the capsaicin analogue, NE-21610 (Procter and Gamble), inactivates nociceptors but not low-threshold mechanoreceptors in monkey. The present study examined the effects of cutaneous NE-21610 on heat and mechanical sensation in normal human volunteers. In the first series of experiments, subjects received intradermal (i.d.) injections (30 μl) of the vehicle alone or with the drug (0.3, 3.0, 10 μg) into different sites on the volar forearm. Subjects were randomly assigned to 1 of 3 protocols to examine drug-evoked pain (n = 8), or alterations in pain to heat (n = 8) or mechanical (n = 8) stimuli induced by the drug. An additional 7 subjects rated pain to mechanical and heat stimuli before and after subcutaneous (s.c.) injections (300 μl) of the vehicle or drug (100 μg). The peak pain occurred at the time of injection, was of short duration, and was similar for vehicle and drug injections. A mild, dose-related pain followed that lasted up to 2 h. Von Frey thresholds for detection, sharpness, and pain at the injection site (measured 24 h after injection) were not significantly altered by either i.d. or s.c. drug administration. However, pain to stepped heat stimuli was reduced in a dose-dependent fashion for both types of injection. At the highest drug doses, analgesia to heat stimuli was still present 1 week after injection. Recovery of heat sensitivity occurred several weeks after injection. This dissociated loss of heat but not mechanical pain sensibility may be due to: (1) a selective action of the drug on heat transducers in nociceptors responsive to both heat and mechanical stimuli, or (2) a selective action on that subset of nociceptors responsible for signaling heat-evoked pain.
AB - Intradermal injection of the capsaicin analogue, NE-21610 (Procter and Gamble), inactivates nociceptors but not low-threshold mechanoreceptors in monkey. The present study examined the effects of cutaneous NE-21610 on heat and mechanical sensation in normal human volunteers. In the first series of experiments, subjects received intradermal (i.d.) injections (30 μl) of the vehicle alone or with the drug (0.3, 3.0, 10 μg) into different sites on the volar forearm. Subjects were randomly assigned to 1 of 3 protocols to examine drug-evoked pain (n = 8), or alterations in pain to heat (n = 8) or mechanical (n = 8) stimuli induced by the drug. An additional 7 subjects rated pain to mechanical and heat stimuli before and after subcutaneous (s.c.) injections (300 μl) of the vehicle or drug (100 μg). The peak pain occurred at the time of injection, was of short duration, and was similar for vehicle and drug injections. A mild, dose-related pain followed that lasted up to 2 h. Von Frey thresholds for detection, sharpness, and pain at the injection site (measured 24 h after injection) were not significantly altered by either i.d. or s.c. drug administration. However, pain to stepped heat stimuli was reduced in a dose-dependent fashion for both types of injection. At the highest drug doses, analgesia to heat stimuli was still present 1 week after injection. Recovery of heat sensitivity occurred several weeks after injection. This dissociated loss of heat but not mechanical pain sensibility may be due to: (1) a selective action of the drug on heat transducers in nociceptors responsive to both heat and mechanical stimuli, or (2) a selective action on that subset of nociceptors responsible for signaling heat-evoked pain.
KW - Flare
KW - Hyperalgesia
KW - Nociceptor
KW - Pain
KW - Psychophysics
KW - Wheal
UR - http://www.scopus.com/inward/record.url?scp=0028942018&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0028942018&partnerID=8YFLogxK
U2 - 10.1016/0304-3959(94)00154-7
DO - 10.1016/0304-3959(94)00154-7
M3 - Article
C2 - 7644243
AN - SCOPUS:0028942018
SN - 0304-3959
VL - 61
SP - 17
EP - 26
JO - Pain
JF - Pain
IS - 1
ER -