Peripheral modulation of pain in conscious guinea pigs: effect of morphine, nalorphine and clonidine.
1. Morphine and nalorphine were shown to have a peripheral analgesic effect on conscious guinea pigs, producing a decrease in the vocalization response to noxious electrical stimulation. Naloxone antagonized the effect of morphine and nalorphine. 2. Locally administered clonidine had a peripheral analgesic effect on conscious guinea pigs, producing a decrease in the vocalization response to noxious electrical stimulation. 3. The peripheral analgesia of clonidine was antagonized by yohimbine and naloxone. The analgesic effect of clonidine was 250-300 times more potent than that of lidocaine. 4. It is suggested that alpha 2-adrenergic receptor agonists may activate enkephalin-like substances released at the peripheral level.
Nakamura
M
M
Departamento de Fisiologia, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Brasil.
Lico
M C
MC
D000698:Analgesia; D000818:Animals; D003000:Clonidine; D004305:Dose-Response Relationship, Drug; D004558:Electric Stimulation; D006168:Guinea Pigs; D007279:Injections, Subcutaneous; D009020:Morphine; D009269:Nalorphine; D010147:Pain Measurement; D014828:Vocalization, Animal
D009020:Morphine; D003000:Clonidine; D009269:Nalorphine