5-HT2A receptor subtype is involved in the thermal hyperalgesic mechanism of serotonin in the periphery.

Abstract

The present study was designed to investigate which subtypes of 5-HT receptors are involved in 5-HT-induced hyperalgesia using behavioral assessment of hyperalgesia. 5-HT and various putative agonists for 5-HT receptor subtypes (5-HT(1A, 2, 3)) were intradermally injected into the rat ipsilateral hindpaw. Paw-withdrawal latency to radiant heat stimulation was examined every 15 min for 2 h. Injection of 5-HT (30 microg) and 5-HT2A receptor agonist (alpha-methyl 5-HT; 0.86 mg/kg) significantly reduced the paw-withdrawal latency. On the other hand, injection of 5-HT3 receptor agonists (2-methyl 5-HT; 0.86 mg/kg, m-CPG; 8 mg/kg) did not produce hyperalgesia. Furthermore, pretreatment with 5-HT2A receptor antagonist (ketanserin), but not with 5-HT3 receptor antagonist (tropisetron), attenuated the behavioral response after the injection of 5-HT. These findings strongly suggest that the 5-HT2A receptor subtype, but not the 5-HT3 subtype, is involved in 5-HT-induced hyperalgesia in acute injury and inflammation in the rat. In situ hybridization histochemistry revealed the presence of 5-HT2 receptor mRNA in a subpopulation of both large and small neurons in the rat dorsal root ganglia.

• Authors: Atsushi Tokunaga, Misako Saika, Emiko Senba
• Journal: Pain (Pain) Vol. 76 Issue 3 Pg. 349-355 (Jun 1998) ISSN: 0304-3959 [Print] United States
• PMID: 9718253 (Publication Type: Journal Article)

Chemical References

• RNA, Messenger
• Receptor, Serotonin, 5-HT2A
• Receptors, Serotonin
• Serotonin Antagonists
• Serotonin Receptor Agonists
• Serotonin

Topics

• Animals
• Behavior, Animal (drug effects)
• Dose-Response Relationship, Drug
• Ganglia, Spinal (drug effects, physiology)
• Hot Temperature
• Hyperalgesia (metabolism, physiopathology)
• In Situ Hybridization
• Male
• Peripheral Nervous System (physiopathology)
• RNA, Messenger (biosynthesis)
• Rats
• Rats, Sprague-Dawley
• Receptor, Serotonin, 5-HT2A
• Receptors, Serotonin (biosynthesis, physiology)
• Serotonin (physiology)
• Serotonin Antagonists (pharmacology)
• Serotonin Receptor Agonists (pharmacology)