Delta-opiod receptor-mediated forced swimming stress-induced antinociception in the formalin test

• Published in: Psychopharmacology Vol. 113; no. 1; p. 15
• Main Authors: Kamei, J, Hitosugi, H, Misawa, M, Nagase, H, Kasuya, Y
• Format: Journal Article
• Language: English
• Published: Germany 01.11.1993
• Subjects: Animals; Formaldehyde; Male; Mice; Mice, Inbred ICR; Naltrexone - analogs & derivatives; Naltrexone - pharmacology; Narcotic Antagonists - pharmacology; Nociceptors - drug effects; Nociceptors - physiology; Pain Measurement - drug effects; Receptors, Opioid, delta - agonists; Receptors, Opioid, delta - antagonists & inhibitors; Receptors, Opioid, delta - physiology; Stress, Psychological - physiopathology; Stress, Psychological - psychology; Swimming
• ISSN: 0033-3158
• DOI: 10.1007/BF02244327

Forced swimming stress-induced antinociception (FSSIA) was assessed using the formalin test. Male ICR mice, weighing about 30 g, were forced to swim in water at 20 degrees C for 3 min. In unstressed mice, SC injection of formalin (0.5%) to the hindpaw caused a biphasic response: an immediate nociceptive response (first phase) followed by a tonic response (second phase). Although forced swimming stress (FSS) had no effect on the duration of the first-phase response, FSS significantly reduced the duration of the second-phase response. The effect of FSSIA on the second-phase response was blocked by naltrindole (1 mg/kg, SC), a selective delta-opioid receptor antagonist, but not by beta-funaltrexamine (20 mg/kg, SC), a selective mu-opioid receptor antagonist. These results indicate that FSS may selectively reduce the second phase of the formalin-induced nociceptive response, primarily through delta-opioid receptors.