Pain in Parkinson's disease (PD) is increasingly recognized as a major factor associated with poor healthrelated quality of life. However, classic therapeutic drugs supplying dopamine have limited therapeutic effect on PD related pain. This suggests that there is a mechanism outside the dopamine system that causes pain in PD. Our previous study has demonstrated that 6-OHDA induced PD model manifested hyperalgesia to thermal and mechanical stimuli and decreased serotonin (5-HT) contents in the spinal dorsal horn (SDH). Several 5-HT receptor subtypes have been con rmed to be associated with nociception in the spinal cord, such as 5-HT1A receptor, 5-HT1B receptor, 5-HT2 receptor, 5-HT3 receptor, and 5-HT7 receptor. Most researches have shown that 5-HT1A receptor and 5-HT3 receptor played a key role in pain transmission in the spinal cord. Thus, we hypothesize that hyperalgesia of 6-OHDA rats may be related to increased excitability of SDH neurons and the functional change of 5-HT3 receptor may reverse the hyperalgesia of 6-OHDA rats and decrease cell excitability of SDH neurons. To test this hypothesis, we used whole-cell patch-clamp and pharmacological methods to evaluate the effect of 5-HT3 receptor and 5-HT1A receptor on the hyperalgesia of 6-OHDA rats. The results suggested that increased excitability in SDH neurons could be reversed by 5-HT3 receptor antagonist ondansetron (20 µmol/L), but not 5-HT3 receptor agonist M-CPBG (30 µmol/L), 5-HT1A receptor antagonist 8-OH DPAT (10 µmol/L)and agonist WAY-100635 (10 µmol/L). Intrathecal injection with ondansetron (0.1 mg/kg) but not M-CPBG (0.1 mg/kg), 8-OH DPAT (0.1 mg/kg) and WAY-100635 (0.1 mg/kg) signi cantly attenuated the mechanical hyperalgesia and thermal hyperalgesia of 6-OHDA rats. Therefore, the present study suggests that inhibition of 5-HT3 receptor relieves hyperalgesia in PD rats by reducing the excitability of SDH neurons. Our study provides a novel mechanism or therapeutic strategy for pain in patients with PD.
Pain in Parkinson’s disease (PD) is increasingly recognized as a major factor associated with poor health-related quality of life. However, classic therapeutic drugs supplying dopamine have limited therapeutic effect on PD related pain. This suggests that there is a mechanism outside the dopamine system that causes pain in PD. Our previous study has demonstrated that 6-OHDA induced PD model manifested hyperalgesia to thermal and mechanical stimuli and decreased serotonin (5-HT) contents in the spinal dorsal horn (SDH). Several 5-HT receptor subtypes have been confirmed to be associated with nociception in the spinal cord, such as 5-HT1A receptor, 5-HT1B receptor, 5-HT2 receptor, 5-HT3 receptor, and 5-HT7 receptor. Most researches have shown that 5-HT1A receptor and 5-HT3 receptor played a key role in pain transmission in the spinal cord. Thus, we hypothesize that hyperalgesia of 6-OHDA rats may be related to increased excitability of SDH neurons and the functional change of 5-HT3 receptor may reverse the hyperalgesia of 6-OHDA rats and decrease cell excitability of SDH neurons. To test this hypothesis, we used whole-cell patch-clamp and pharmacological methods to evaluate the effect of 5-HT3 receptor and 5-HT1A receptor on the hyperalgesia of 6-OHDA rats. The results suggested that increased excitability in SDH neurons could be reversed by 5-HT3 receptor antagonist ondansetron (20 µmol/L), but not 5-HT3 receptor agonist M-CPBG (30 µmol/L), 5-HT1A receptor antagonist 8-OH DPAT (10 µmol/L)and agonist WAY-100635 (10 µmol/L). Intrathecal injection with ondansetron (0.1 mg/kg) but not M-CPBG (0.1 mg/kg), 8-OH DPAT (0.1 mg/kg) and WAY-100635 (0.1 mg/kg) significantly attenuated the mechanical hyperalgesia and thermal hyperalgesia of 6-OHDA rats. Therefore, the present study suggests that inhibition of 5-HT3 receptor relieves hyperalgesia in PD rats by reducing the excitability of SDH neurons. Our study provides a novel mechanism or therapeutic strategy for pain in patients with PD.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.