Sensitization of primary afferents to mechanical and heat stimuli after incision in a novel in vitro mouse glabrous skin-nerve preparation.
In this study, we recorded activity from afferent fibers innervating the mouse plantar skin, the same region evaluated in pain behavior experiments. We compared responses of afferents from incised and unincised hind paw skin. The plantar skin together with attached medial and lateral plantar nerves was dissected until they could be completely removed intact and placed in an organ bath chamber continuously perfused with oxygenated Kreb's solution with the temperature maintained at 32 degrees C. Afferent nerve activities to feedback-controlled mechanical and heat stimuli and cooling were recorded. Eighty-five single Adelta- and C-fiber afferents were recorded, 42 from control and the remainder from incised animals. A greater proportion of C-fibers (11/34) from incised skin had spontaneous activity than in the unincised preparation (2/32). The mechanical thresholds of both Adelta- and C-fiber units were not different between control and incised groups but the responses to suprathreshold mechanical stimulation were increased in low threshold Adelta- and C-fibers. The greatest change in heat sensitivity was apparent when multi-fiber total activity was measured; threshold was reduced, total spikes were greater and the peak discharge frequency was increased. In summary, feedback-controlled stimulation identified mechanical sensitization after incision in an in vitro preparation. Few fibers were excited by cooling. Heat sensitization of primary afferents was more prominent when activities of unclassified afferents are included. The preparation allows us to study afferent function of the same tissue that is examined for in vivo pain behavior assays in mice.
Banik
Ratan K
RK
Departments of Anesthesia and Pharmacology, University of Iowa Hospitals and Clinics, Iowa City, IA 52242, USA Pain Research Program, New Jersey Neuroscience Institute at John F. Kennedy Medical Center, 65 James Street, Edison, NJ 08820, USA.
Brennan
Timothy J
TJ
D000818:Animals; D006358:Hot Temperature / Q000009:adverse effects; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D036421:Nerve Fibers, Unmyelinated / Q000502:physiology; D009475:Neurons, Afferent / Q000502:physiology*; D009924:Organ Culture Techniques; D010147:Pain Measurement / Q000379:methods; D010812:Physical Stimulation / Q000379:methods; D012879:Skin Physiological Phenomena; D013979:Tibial Nerve / Q000502:physiology