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Updated: Aug 15, 2026

A Simple and Inexpensive Method for Determining Cold Sensitivity and Adaptation in Mice
Published on: March 17, 2015
5-HT2A receptor subtype is involved in the thermal hyperalgesic mechanism of serotonin in the periphery
Atsushi Tokunaga1, Misako Saika, Emiko Senba
1Department of Anatomy and Neurobiology, Wakayama Medical College, 27 Kyuban-cho, Wakayama 640-8155, Japan.
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.
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