What effect do SSRIs have on the expression of the ligand-gated ion channel, the 5-HT3 receptor?
SSRI's theoretically increase Serotonin levels. Serotonin is an agonist to the 5HT-3 receptors. The 5HT-3a primarily associated with the upper gut and the 5HT-3b with the lower gut. I would guess that theoretically again, SSRI's would tend to increase nausea, emesis, and diarrhea. There may be other effects, but these are the ones I have researched.
The anti-emetics Dolasetron, Ondansetron, Granisetron, and Tropisetron are 5HT-3 antagonists.