Laser irradiation abates neuronal responses to nociceptive stimulation of rat-paw skin.
The effects of diode laser irradiation on peripheral nerves was examined by monitoring neuronal discharges elicited by application of various stimuli to the hind-paw skin of rats. Neuronal discharges elicited by brush, pinch, cold, and/or heat stimulation, as well as chemical stimulation by injection of turpentine (0.1 ml, SC) were recorded from L5 dorsal roots in urethane-anesthetized rats. Diode laser irradiation (830 nm, 40 mW, 3 min, continuous wave) of the saphenous nerve exposed from the muscle of the lower leg significantly inhibited neuronal discharges elicited by pinch (68.4 +/- 6.5%), cold (45.4 +/- 9.2%), and heat stimulation (49.2 +/- 11.3%). Neuronal discharges induced by brush stimulation (104.3 +/- 4.7%) were not affected by laser irradiation. Injection of turpentine, a chemical irritant, into the hind-paw skin (0.1 ml, SC) elicited neuronal discharges in the ipsilateral dorsal root, and these discharges were significantly inhibited or abolished by laser irradiation. In 6- to 7-week-old rats treated neonatally with capsaicin (10 mg/kg, SC), injection of turpentine into the hind-paw skin did not elicit neuronal discharges and laser irradiation did not affect the background discharges. These data suggest that laser irradiation may selectively inhibit nociceptive neuronal activities.
Tsuchiya
K
K
Department of Physiology, School of Medicine, Showa University, Tokyo, Japan.
Kawatani
M
M
Takeshige
C
C
Matsumoto
I
I
D000818:Animals; D000831:Animals, Newborn; D003080:Cold Temperature; D005071:Evoked Potentials / Q000187:drug effects / Q000502:physiology; D005260:Female; D006358:Hot Temperature; D007834:Lasers; D008297:Male; D009411:Nerve Endings / Q000502:physiology / Q000528:radiation effects; D009474:Neurons / Q000528:radiation effects*; D009619:Nociceptors / Q000502:physiology / Q000528:radiation effects*; D010146:Pain / Q000139:chemically induced / Q000503:physiopathology; D010525:Peripheral Nerves / Q000502:physiology / Q000528:radiation effects*; D010812:Physical Stimulation; D051381:Rats; D017208:Rats, Wistar; D012867:Skin / Q000294:innervation* / Q000528:radiation effects*; D014425:Turpentine
D014425:Turpentine