Area 3a neuron response to skin nociceptor afferent drive.
Area 3a neurons are identified that respond weakly or not at all to skin contact with a 25-38 degrees C probe, but vigorously to skin contact with the probe at > or =49 degrees C. Maximal rate of spike firing associated with 1- to 7-s contact at > or =49 degrees C occurs 1-2 s after probe removal from the skin. The activity evoked by 5-s contact with the probe at 51 degrees C remains above-background for approximately 20 s after probe retraction. After 1-s contact at 55-56 degrees C activity remains above-background for approximately 4 s. Magnitude of spike firing associated with 5-s contact increases linearly as probe temperature is increased from 49-51 degrees C. Intradermal capsaicin injection elicits a larger (approximately 2.5x) and longer-lasting (100x) increase in area 3a neuron firing rate than 5-s contact at 51 degrees C. Area 3a neurons exhibit enhanced or novel responsivity to 25-38 degrees C contact for a prolonged time after intradermal injection of capsaicin or alpha, beta methylene adenosine triphosphate. Their 1) delayed and persisting increase in spike firing in response to contact at > or =49 degrees C, 2) vigorous and prolonged response to intradermal capsaicin, and 3) enhanced and frequently novel response to 25-38 degrees C contact following intradermal algogen injection or noxious skin heating suggest that the area 3a neurons identified in this study contribute to second pain and mechanical hyperalgesia/allodynia.
Whitsel
Barry L
BL
Department of Biomedical Engineering, University of North Carolina, School of Medicine, Chapel Hill, NC 27599-7545, USA. bwhitsel@med.unc.edu
Favorov
Oleg V
OV
Li
Yongbiao
Y
Quibrera
Miguel
M
Tommerdahl
Mark
M
D000255:Adenosine Triphosphate / Q000031:analogs & derivatives; D000772:Anesthesia, Local; D000818:Animals; D002211:Capsaicin; D004594:Electrophysiology; D005260:Female; D005528:Foot / Q000294:innervation / Q000502:physiology; D006225:Hand / Q000294:innervation / Q000502:physiology; D006358:Hot Temperature; D008297:Male; D009475:Neurons, Afferent / Q000502:physiology*; D009619:Nociceptors / Q000187:drug effects / Q000502:physiology*; D010146:Pain / Q000139:chemically induced / Q000503:physiopathology; D010296:Parietal Lobe / Q000166:cytology / Q000502:physiology*; D010812:Physical Stimulation; D012453:Saimiri; D012867:Skin / Q000294:innervation*; D013003:Somatosensory Cortex / Q000166:cytology / Q000502:physiology*
D000255:Adenosine Triphosphate; C002630:alpha,beta-methyleneadenosine 5'-triphosphate; D002211:Capsaicin