Plasticity of emesis to a 5-HT3 agonist: effect of order of visceral nerve cuts

Serotonin type 3 receptors are critical for vomiting induced by radiation and cancer chemotherapy. To investigate the mechanisms involved, we analyzed the effects of abdominal visceral denervation using cats. Thresholds for vomiting induced by the serotonin-3 receptor agonist phenylbiguanide varied depending on the order of chronic nerve transections. Lower thoracic vagotomy, splanchnicectomy, and their sequential combination increased thresholds. However, when splanchnicectomy, which causes a large increase in threshold, was followed 14-51 days later by vagotomy, thresholds dropped by an average of 40%. These results demonstrate plasticity in, and potential for modulation of, the emetic reflex.