Ca2+/CaMKII‐dependent ERK1/2 signaling mediates serotonin 5‐HT3 receptor‐mediated vomiting (LB742)

Abstract

The 5‐HT3R agonist 2‐Me‐5‐HT induces vomiting. Its downstream signaling remain unknown. 5‐HT3R has high permeability to extracellular Ca2+ and upon stimulation allows Ca2+ influx. We examined the contribution of Ca2+/CaMKIIα, interaction of 5‐HT3R with calmodulin, and ERK1/2 signaling to 2‐Me‐5‐HT‐induced emesis in least shrews. 2‐Me‐5‐HT augmented intracellular Ca2+ levels in the brainstem slices and the 5‐HT3R antagonist palonosetron, abolished the response. Pre‐treatment with either: i) amlodipine, an antagonist that blocks L‐type Ca2+ channels; ii) dantrolene, an inhibitor of ryanodine receptors (RyRs); iii) a combination of their less‐effective doses; or iv) inhibitors of CaMKII (KN93) and ERK1/2 (PD98059); dose‐dependently suppressed emesis. 2‐Me‐5‐HT also: i) enhanced the interaction of 5‐HT3R with calmodulin in the brainstem as revealed by immunoprecipitation, and their colocalization in the area postrema and intestine by immunohistochemistry; and ii) activated CaMKIIα in brainstem and enterochromaffin cells as shown by western blot and immunocytochemistry. These effects were suppressed by the 5‐HT3R antagonist, palonosetron. 2‐Me‐5‐HT treatment also activated ERK1/2 in brainstem, which was abrogated by palonosetron, KN93, PD98059, amlodipine, dantrolene, or a combination of amlodipine plus dantrolene. However, blockade of ER IP3Rs by 2‐APB, had no significant effect on these parameters. Thus, Ca2+ mobilization via extracellular Ca2+ influx through 5‐HT3Rs/L‐type Ca2+ channels and Ca2+ release via RyRs on ER, initiate a Ca2+‐dependent sequential activation of CaMKIIα and ERK1/2, which contribute to the 2‐Me‐5‐HT‐evoked emesis.Grant Funding Source: COMP/WesternU startup funds