| 18295406 |
Qu CL, Huo FQ, Huang FS, Li YQ, Tang JS, Jia H: The role of 5-HT receptor subtypes in the ventrolateral orbital cortex of 5-HT-induced antinociception in the rat. Neuroscience. 2008 Mar 18;152(2):487-94. Epub 2007 Sep 21.
The present study examined the involvement of 5-HT in the ventrolateral orbital cortex (VLO) on descending antinociception and determined which subtypes of 5-HT receptors mediated this effect. This study focused on the effects of 5-HT microinjection in the VLO of lightly anesthetized male rats on the radiant heat-evoked tail flick (TF) reflex, as well as the influence of 5-HT (1A), 5-HT (2), 5-HT (3), and 5-HT (4) receptor subtype antagonists on the effect of 5-HT. Results showed that 5-HT microinjection (2, 5, 10 microg, in 0.5 microl) into the VLO depressed the TF reflex in a dose-dependent manner. Pretreatment with 5-HT receptor antagonists (1-(2-methoxyphenyl)-4-[4-(2-phthalimido) butyl] piperazine hydrobromide (NAN-190), cyproheptadine hydrochloride (CPT) and 1-methyl-N-(8-methyl-8-azabicyclo [3.2.3]-oct-3-yl)-1H-indazole-3-carboxami de maleate salt (LY-278,584)), specific for 5-HT (1A), 5-HT (2) and 5-HT (3) receptors, respectively, partially reversed the 5-HT-evoked inhibition. In contrast, the 5-HT (4) receptor antagonist, 1-[2-[(methylsulfonyl)-amino] ethyl]-4-piperidinyl] methyl1-methyl-1H-indole -3-carboxylate (GR 113808), had no effect on the inhibition of 5-HT. Microinjections of NAN-190, CPT and LY-278,584 alone into the VLO had no effect on the TF reflex. These results suggest that 5-HT (1A), 5-HT (2) and 5-HT (3), but not 5-HT (4) receptors, are involved in mediating 5-HT-induced antinociception in the VLO. According to different properties and distribution patterns of the 5-HT receptor subtypes on neurons, the possible mechanism of 5-HT activation of the VLO-periaqueductal gray (PAG) descending antinociceptive pathway is discussed. |
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