the discomfort associated with irritable bowel syndrome can be alleviated with low doses of the class of antidepressants that block the reuptake of serotonin from the synaptic cleft (the space between adjacent neurons). serotonin is a relatively small polar neurotransmitter used to transmit nerve impulses in the nerve tissue in the gut and central nervous system. serotonin is transported back into the releasing neuron up its concentration gradient and down a sodium gradient. how might an antidepressant block serotonin reuptake by the releasing neuron?