Cardamonin Modulates Neuropathic Pain through the Possible Involvement of Serotonergic 5-HT1A Receptor Pathway in CCI-Induced Neuropathic Pain Mice Model

Cardamonin, a naturally occurring chalcone isolated from Alpinia species has shown to possess strong anti-inflammatory and anti-nociceptive activities. Previous studies have demonstrated that cardamonin exerts antihyperalgesic and antiallodynic properties in chronic constriction injury (CCI)-induced neuropathic pain animal model. However, the mechanisms underlying cardamonin’s effect have yet to be fully understood. The present study aims to investigate the involvement of the serotonergic system in cardamonin induced antihyperalgesic and antiallodynic effects in CCI-induced neuropathic pain mice model. The neuropathic pain symptoms in the CCI mice model were assessed using Hargreaves Plantar test and von-Frey filament test on day 14 post-surgery. Central depletion of serotonin along the descending serotonergic pathway was done using ρ-chlorophenylalanine (PCPA, 100 mg/kg, i.p.), an inhibitor of serotonin synthesis for four consecutive days before cardamonin treatment, and was found to reverse the antihyperalgesic and antiallodynic effect produced by cardamonin. Pretreatment of the mice with several 5-HT receptor subtypes antagonists: methiothepin (5-HT1/6/77 receptor antagonist, 0.1 mg/kg), WAY 100635 (5-HT1A receptor antagonist, 1 mg/kg), isamoltane (5-HT1B receptor antagonist, 2.5 mg/kg), ketanserin (5-HT2A receptor antagonist, 0.3 mg/kg), and ondansetron (5-HT3 receptor antagonist, 0.5 mg/kg) were shown to abolish the effect of cardamonin induced antihyperalgesic and antiallodynic effects. Further evaluation of the 5-HT1A receptor subtype protein expressions reveals that cardamonin significantly upregulated its expression in the brainstem and spinal cord. Our results suggest that the serotonergic pathway is essential for cardamonin to exert its antineuropathic effect in CCI mice through the involvement of the 5-HT1A receptor subtype in the central nervous system.

N-3 Polyunsaturated Fatty Acid Improved Depression via Neuroendocrine and Serotonergic System in Post-Menopausal Rats with Maternal Separation and Chronic Mild Stress

Objectives The purpose of the present study was to investigate the hypothesis that lifetime n-3 polyunsaturated fatty acids (PUFA) intake improved depression through serotonergic pathway in post-menopausal rats with chronic mild stress (CMS) and maternal separation (MS). Methods Female rats were fed diets with 0% or 1 energy % n-3 PUFA during lifetime from embryonic day (ED) 0 to postnatal day (PND) 112, or 1% n-3 PUFA before weaning (ED 0-PND 20), or after weaning (PND 20–112). The rats in four diet group were allocated to brief separation from dam (non-MS group) or long-term separation (MS group) on PND 2–14, and then underwent CMS on PND 91–105 after ovariectomy. Thus, there were eight groups in total (n = 8/group). Results MS + CMS increased depressive behaviors, and modified hypothalamic-pituitary-adrenal (HPA) axis activity, inflammation, serotonergic and glutamatergic neurotransmission, and related miRNAs as compared to CMS alone. N-3 PUFA decreased depressive behaviors by decreasing immobility while increasing swimming during forced swim test, and increasing sucrose preference in rats with MS + CMS and with CMS. N-3 PUFA decreased HPA axis activity by modifying expressions of corticotrophin releasing factor and glucocorticoid receptor, and levels of adrenocorticotropic hormone and corticosterone. N-3 PUFA also reduced levels of TNF-α, IL-1β, IL-6, PGE2, and miRNA-218, and increased serotonergic neurotransmission, including expressions of cAMP response element binding protein, brain-derived neurotrophic factor and serotonin 1A receptor, and serotonin level, and expression of miRNA-155. In addition, lifetime supplementation of n-3 PUFA had greater effect than pre- or post-supplementation. N-3 PUFA had no effect on glutamatergic pathway including α-amino-3-hydroxy-5-methyl-4-isoxazole propionate receptor and N-methyl-D-aspartate receptor. Conclusions The present study suggested that lifetime n-3 PUFA improved depression in post-menopausal rats with MS + CMS through modulation of serotonergic pathway by decreasing HPA axis activity but not glutamatergic pathway. Funding Sources This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (NRF-2018R1A2B6002486).