Differential antinociceptive effect of transcutaneous electrical stimulation on pain behavior sensitive or insensitive to phentolamine in neuropathic rats.
The effects of transcutaneous electrical stimulation and systemic injection of phentolamine, a non-specific alpha-adrenergic antagonist, on the behavioral signs of mechanical allodynia and cold hyperalgesia in rats with nerve injury were investigated. Mechanical allodynia and cold hyperalgesia were evaluated by measuring the paw withdrawal frequency (PWF) resulting from repetitive application of a von Frey hair and the paw lift duration (PLD) at a cold temperature, respectively. After a unilateral nerve injury, both PWF and PLD increased in the injured hind paw. Application of low-frequency, high-intensity transcutaneous electrical stimulation (LFHI-TES) to the injured hind paw depressed the injury-induced increased PWF, whereas it had no effect on the injury-induced increased PLD. Naloxone reversed the LFHI-TES produced depression of PWF. Intraperitoneal administration of phentolamine depressed the injury-induced increased PLD without affecting the injury-induced increased PWF. Our results suggest that LFHI-TES, which activates the endogenous opioid systems, produces an antinociceptive effect that appears to be related to whether or not the pain is mediated by sympathetic activity.
Nam
T S
TS
Department of Physiology, Yonsei University College of Medicine, C.P.O. Box 8044, 120-752, Seoul, South Korea.
Choi
Y
Y
Yeon
D S
DS
Leem
J W
JW
Paik
K S
KS
D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology*; D000818:Animals; D003080:Cold Temperature; D006614:Hindlimb / Q000187:drug effects; D006930:Hyperalgesia / Q000628:therapy*; D008297:Male; D010147:Pain Measurement / Q000187:drug effects* / Q000379:methods; D010523:Peripheral Nervous System Diseases / Q000628:therapy*; D010646:Phentolamine / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013127:Spinal Nerves / Q000293:injuries; D014110:Touch; D004561:Transcutaneous Electric Nerve Stimulation
D000317:Adrenergic alpha-Antagonists; D010646:Phentolamine